Publications HAL de Franck, Laloë ; F. Laloë du labo/EPI LKB; Laboratoire Kastler Brossel; Laboratoire de Spectroscopie Hertzienne de l'ENS; UMR 8552

2022

Journal articles

titre
Gravitational quantum collapse in dilute systems
auteur
Franck Laloë
article
Comptes Rendus. Physique, 2022, 23 (G1), pp.27-40. ⟨10.5802/crphys.104⟩
DOI
DOI : 10.5802/crphys.104
Accès au bibtex
https://arxiv.org/pdf/2205.08463 BibTex

Book sections

titre
Quantum mechanics is routinely used in laboratories with great success, but no consensus on its interpretation has emerged
auteur
Franck Laloë
article
The Oxford handbook of The history of quantum interpretations, chatpter 1. O Freire Jr Editor, 2022
Accès au bibtex
BibTex

2021

Journal articles

titre
The outcomes of measurements in the de Broglie–Bohm theory
auteur
Geneviève Tastevin, Franck Laloë
article
Comptes Rendus. Physique, 2021, 22 (1), pp.99-116. ⟨10.5802/crphys.81⟩
resume
Within the de Broglie-Bohm (dBB) theory, the measurement process and the determination of its outcome are usually discussed in terms of the effect of the Bohmian positions of the measured system S. %} This article shows that the Bohmian positions associated with the measurement apparatus M can actually play a crucial role in the determination of the result of measurement. Indeed, in many cases, the result is practically independent of the initial value of a Bohmian position associated with S, and determined only by those of M. The measurement then does not reveal the value of any pre-existing variable attached to S, but just the initial state of the measurement apparatus. Quantum contextuality then appears with particular clarity as a consequence of the dBB dynamics for entangled systems.
DOI
DOI : 10.5802/crphys.81
Accès au texte intégral et bibtex
https://hal.science/hal-03343510/file/2102.02519 BibTex

Books

titre
Symétries continues
auteur
Franck Laloë
article
EDP Sciences, 2021, collections "Savoirs acruels", Michèle Leduc, Michel le Bellac, 978-2-7598-2631-5
resume
Les groupes de symétrie, ou groupes d’invariance, jouent un rôle important dans toute la physique. Les translations d’espace et de temps, les rotations d’espace et enfin les transformations de Galilée ou de Lorentz entre référentiels d’inertie définissent la structure de l’espace-temps. Les symétries correspondantes sont tout particulièrement importantes en mécanique quantique. En effet les opérateurs fondamentaux - énergie, position, impulsion, moment angulaire - ainsi que leurs relations de commutation, loin d’être arbitraires, sont déterminés par la géométrie de l’espace et celle de l’espace-temps. Ces considérations de symétrie permettent de comprendre l’origine de la masse et du spin et d’établir des équations d’onde comme l’équation de Schrödinger ou celle de Dirac à partir du groupe d’invariance choisi : Galilée ou Lorentz. Ces équations permettent de décrire les particules de spin 1/2 et prédisent correctement leur moment magnétique anormal. Cet ouvrage, issu d’un cours de DEA de Physique théorique de l’ENS, a à la fois un caractère fondamental et appliqué. L’utilisation des symétries, et en particulier de celle de rotation, est un outil pratique permettant une approche géométrique de problèmes comme le théorème de Wigner-Eckart ou les opérateurs tensoriels irréductibles. Enfin le livre discute de deux symétries discrètes, la parité et le renversement du temps.
Accès au bibtex
BibTex

2020

Journal articles

titre
A model of quantum collapse induced by gravity
auteur
Franck Laloë
article
The European Physical Journal D : Atomic, molecular, optical and plasma physics, 2020, 74 (2), ⟨10.1140/epjd/e2019-100434-1⟩
resume
We discuss a model where a spontaneous quantum collapse is induced by the gravitational interaction, treated classically. Its dynamics couples the standard wave function of a system with the Bohmian positions of its particles, which are considered as the only source of the gravitational attraction. The collapse is obtained by adding a small imaginary component to the gravitational coupling. It predicts extremely small perturbations of microscopic systems, but very fast collapse of QSMDS (quantum superpositions of macroscopically distinct quantum states) of a solid object, varying as the fifth power of its size. The model does not require adding any dimensional constant to those of standard physics.
DOI
DOI : 10.1140/epjd/e2019-100434-1
Accès au bibtex
https://arxiv.org/pdf/1905.12047 BibTex

Books

titre
Quantum Mechanics, vol III
auteur
Claude Cohen-Tannoudji, Bernard Diu, Franck Laloë
article
Wiley, 2020, 978-3-527-34555-7
Accès au bibtex
BibTex
titre
Quanten-Mechanik, Band III
auteur
Claude Cohen-Tannoudji, Bernard Diu, Franck Laloë
article
de Gruyter, 2020, 978-3-11-062064-1
Accès au bibtex
BibTex
titre
Kvantovaia Mekannika, 3
auteur
Claude Cohen-Tannoudji, Bernard Diu, Franck Laloë
article
2020, 978-5-9710-5593-8
Accès au bibtex
BibTex

2019

Journal articles

titre
Quantum collapse dynamics with attractive densities
auteur
Franck Laloë
article
Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2019, 99 (5), ⟨10.1103/PhysRevA.99.052111⟩
resume
We discuss a model of spontaneous collapse of the quantum state that does not require adding any stochastic processes to the standard dynamics. The additional ingredient with respect to the wave function is a position in the configuration space, which drives the collapse in a completely deterministic way. This new variable is equivalent to a set of positions of all the particles, i.e. a set of Bohmian positions, which obey the usual guiding equation of Bohmian theory. Any superposition of quantum states of a macroscopic object occupying different regions of space is projected by a localization process onto the region occupied by the positions. Since the Bohmian positions are well defined in a single realization of the experiment, a space localization into one region is produced. The mechanism is based on the correlations between these positions arising from the cohesive forces inside macroscopic objects. With appropriate values of the two parameters of the model, we check that the corresponding dynamics rapidly projects superpositions of macroscopic states localized in different regions of space into a single region, while is keeps a negligible effect in all situations where the predictions of standard quantum dynamics are known to be correct. The possible relations with gravity are briefly speculated. We then study the evolution of the density operator and a mean-field approximation of the dynamical equations of this model, as well as the change of the evolution of the momentum introduced by the localization process. Possible theoretical interpretations are finally discussed. Generally speaking, this model introduces a sharper border between the quantum and classical world than the GRW and CSL theories, and leaves a broader range of acceptable values for the parameters.
DOI
DOI : 10.1103/PhysRevA.99.052111
Accès au bibtex
https://arxiv.org/pdf/1901.08016 BibTex

Books

titre
Mécanique quantique, tome III, 2e édition
auteur
Claude Cohen-Tannoudji, Bernard Diu, Franck Laloë
article
EDPS; CNRS Editions, 2019, Savoirs Actuels, Michèle Leduc, Michel le Bellac
Accès au bibtex
BibTex
titre
Do we really understand quantum mechanics? 2nd edition
auteur
Franck Laloë
article
Cambridge University Press, 2019, 9781 108477000
resume
Quantum mechanics impacts on many areas of physics from pure theory to applications. However it is difficult to interpret, and philosophical contradictions and counter-intuitive results are apparent at a fundamental level. This book presents our current understanding of the theory, providing a historical introduction and discussing many of its interpretations. Fully revised from the first edition, this book includes state-of-the-art research including loophole free experimental Bell test and theorems on the reality of the wave function including the PBR theorem and a new section on quantum simulation. More interpretations are now included, and these are described and compared, including discussion of their successes and difficulties. Other sections have been expanded, including quantum error correction codes and the reference section. It is ideal for researchers in physics and maths, and philosophers of science interested in quantum physics and its foundations.
Accès au bibtex
BibTex

Preprints, Working Papers, ...

titre
A model of quantum collapse induced by gravity
auteur
F. Laloë
article
2019
resume
We discuss a model where a spontaneous quantum collapse is induced by the gravitational interaction, treated classically. Its dynamics couples the standard wave function of a system with the Bohmian positions of its particles, which are considered as the only source of the gravitational attraction. The collapse is obtained by adding a small imaginary component to the gravitational coupling. It predicts extremely small perturbations of microscopic systems, but very fast collapse of QSMDS (quantum superpositions of macroscopically distinct quantum states) of a solid object, varying as the fifth power of its size. The model does not require adding any dimensional constant to those of standard physics.
Accès au bibtex
https://arxiv.org/pdf/1905.12047 BibTex

2018

Journal articles

titre
Surrealistic Bohmian trajectories do not occur with macroscopic pointers
auteur
G. Tastevin, F. Laloë
article
The European Physical Journal D : Atomic, molecular, optical and plasma physics, 2018, 72, pp.183. ⟨10.1140/epjd/e2018-90129-4⟩
resume
We discuss whether position measurements in quantum mechanics can be contradictory with Bohmian trajectories, leading to what has been called "surrealistic trajectories" in the literature. Previous work has considered that a single Bohmian position can be ascribed to the pointer. Nevertheless, a correct treatment of a macroscopic pointer requires that many particle positions should be included in the dynamics of the system, and that statistical averages should be made over their random initial values. Using numerical as well as analytical calculations, we show that these surrealistic trajectories exist only if the pointer contains a small number of particles; they completely disappear with macroscopic pointers. With microscopic pointers, non-local effects of quantum entanglement can indeed take place and introduce unexpected trajectories, as in Bell experiments; moreover, the initial values of the Bohmian positions associated with the measurement apparatus may influence the trajectory of the test particle, and determine the result of measurement. Nevertheless, a detailed observation of the trajectories of the particles of the pointer can still reveal the nature of the trajectory of the test particle; nothing looks surrealistic if all trajectories are properly interpreted.
DOI
DOI : 10.1140/epjd/e2018-90129-4
Accès au texte intégral et bibtex
https://hal.science/hal-01913349/file/1802.03783 BibTex

2017

Books

titre
Mécanique Quantique, tome III
auteur
Claude Cohen-Tannoudji, Bernard Diu, Franck Laloë
article
EDPS; CNRS Editions, 2017, Savoirs Actuels, 978-2-7598-2107-5
Accès au bibtex
BibTex
titre
Comprenons-nous vraiment la mécanique quantique? 2e édition
auteur
Franck Laloë
article
EDP Sciences, 2017, Michèle Leduc, Michel le Bellac, 978-2-7598-2184-6
resume
La mécanique quantique est à la base de notre compréhension actuelle des lois de la Nature, qu'elles s'appliquent à l'Univers entier, aux objets à notre échelle, ou microscopiques. Toujours vérifiée par l’expérience, elle a permis de nombreuses découvertes et la mise au point de nombreux dispositifs tels que laser, transistor, capteurs pour la photo et la vidéo, etc. Alors, pourquoi se poser la question "comprenons-nous vraiment la mécanique quantique?". C'est qu’une bonne utilisation de la théorie ne signifie pas toujours une véritable compréhension. Le physicien qui prend du recul s'aperçoit parfois que le merveilleux outil intellectuel créé par les scientifiques semble parfois leur échapper, prenant une vie propre et mettant en lumière maints aspects inattendus que ses inventeurs n'avaient pas soupçonnés. L'objet de ce livre est donc de discuter les fondements de la mécanique quantique. On y trouvera un exposé historique sur la naissance des concepts quantiques, leur développement, l'impact des idées de Bell et de son théorème, et leur application récente à de nombreux domaines. Un panorama général des différentes interprétations est présenté en dernière partie. L'ouvrage est accessible à toute personne ayant une formation scientifique générale. Si des équations mathématiques apparaissent parfois, les idées importantes sont contenues dans les commentaires et les figures, l'accent étant mis sur les idées et concepts généraux. Le spécialiste pourra cependant se reporter à une bibliographie très fournie. L'auteur appartient au Laboratoire Kastler Brossel, l'un des laboratoires de physique quantique les plus prestigieux du monde entier, comme l'a montré l'attribution de deux prix Nobel. Avec C. Cohen-Tannoudji et B. Diu, il est également co-auteur d'un ouvrage de mécanique quantique qui est devenu un classique dans les universités françaises et étrangères.
Accès au bibtex
BibTex

2015

Journal articles

titre
Interference Effects in Potential-Wells
auteur
W.J. Mullin, Franck Laloë
article
Physical Review X, 2015, 91, pp.053629. ⟨10.1103/PhysRevA.91.053629⟩
resume
We propose using an array of potential wells as an interferometer, in which the beam splitters are provided by tunneling during an appropriate time through the barrier between wells. This arrangement allows demonstration of generalized Hong-Ou-Mandel effects with multiple particles traversing one or several beam splitters. Other interferometer effects can occur, including a violation of the Bell-Clauser-Horne-Shimony-Holt form of the Bell inequality. With interactions, one sees various effects including so-called fermionization, collective tunneling, and self-trapping.
DOI
DOI : 10.1103/PhysRevA.91.053629
Accès au bibtex
https://arxiv.org/pdf/1503.04183 BibTex
titre
Modified Schrödinger dynamics with attractive densities
auteur
Franck Laloë
article
The European Physical Journal D : Atomic, molecular, optical and plasma physics, 2015, 69 (6), ⟨10.1140/epjd/e2015-60222-5⟩
resume
The linear Schrodinger equation does not predict that macroscopic bodies should be located at one place only, or that:, the outcome of a measurement:, shoud be unique. Quantum mechanics textbooks generally solve the problem by introducing the projection postulate, which forces definite values to emerge during measurements; many other interpretations have also been proposed. Here, in the same spirit as the GRW and CSL theories, we modify the Schrodinger equation in a way that efficiently cancels macroscopic density fluctuations in space. Nevertheless, we do not assume a stochastic dynamics as in GRW or CSL tI eories. Instead, we propose a deterministic evolution that includes an attraction terni towards the averaged density in space of the de Broglie-Bohm position of particles, and show that this is sufficient to ensure macroscopic uniqueness and compatibility with the Born rule. The state vector can then be seen as directly related to physical reality.
DOI
DOI : 10.1140/epjd/e2015-60222-5
Accès au bibtex
https://arxiv.org/pdf/1502.06518 BibTex

2014

Journal articles

titre
Statistical estimation of mechanical parameters of clarinet reeds using experimental and numerical approaches
auteur
Pierre-André Taillard, Franck Laloë, Michel Gross, Jean-Pierre Dalmont, Jean Kergomard
article
Acta Acustica united with Acustica, 2014, 100 (3), pp.555-573. ⟨10.3813/AAA.918735⟩
resume
A set of 55 clarinet reeds is observed by holography, collecting 2 series of measurements made under 2 different moisture contents, from which the resonance frequencies of the 15 first modes are deduced. A statistical analysis of the results reveals good correlations, but also significant differences between both series. Within a given series, flexural modes are not strongly correlated. A Principal Component Analysis (PCA) shows that the measurements of each series can be described with 3 factors capturing more than $90\%$ of the variance: the first is linked with transverse modes, the second with flexural modes of high order and the third with the first flexural mode. A forth factor is necessary to take into account the individual sensitivity to moisture content. Numerical 3D simulations are conducted by Finite Element Method, based on a given reed shape and an orthotropic model. A sensitivity analysis revels that, besides the density, the theoretical frequencies depend mainly on 2 parameters: $E_L$ and $G_{LT}$. An approximate analytical formula is proposed to calculate the resonance frequencies as a function of these 2 parameters. The discrepancy between the observed frequencies and those calculated with the analytical formula suggests that the elastic moduli of the measured reeds are frequency dependent. A viscoelastic model is then developed, whose parameters are computed as a linear combination from 4 orthogonal components, using a standard least squares fitting procedure and leading to an objective characterization of the material properties of the cane \textit{Arundo donax}.
DOI
DOI : 10.3813/AAA.918735
Accès au texte intégral et bibtex
https://hal.science/hal-00668277/file/taillard_12.pdf BibTex
titre
Heating of trapped ultracold atoms by collapse dynamics
auteur
Franck Laloë, W.J. Mullin
article
Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2014, 90, pp.052119. ⟨10.1103/PhysRevA.90.052119⟩
resume
The Continuous Spontaneous Localization (CSL) theory alters the Schr\"odinger equation. It describes wave function collapse as a dynamical process instead of an ill-defined postulate, thereby providing macroscopic uniqueness and solving the so-called measurement problem of standard quantum theory. CSL contains a parameter λ giving the collapse rate of an isolated nucleon in a superposition of two spatially separated states and, more generally, characterizing the collapse time for any physical situation. CSL is experimentally testable, since it predicts some behavior different from that predicted by standard quantum theory. One example is the narrowing of wave functions, which results in energy imparted to particles. Here we consider energy given to trapped ultra-cold atoms. Since these are the coldest samples under experimental investigation, it is worth inquiring how they are affected by the CSL heating mechanism. We examine the CSL heating of a BEC in contact with its thermal cloud. Of course, other mechanisms also provide heat and also particle loss. From varied data on optically trapped cesium BEC's, we present an energy audit for known heating and loss mechanisms. The result provides an upper limit on CSL heating and thereby an upper limit on the parameter λ. We obtain λ≲1(±1)×10−7sec−1.
DOI
DOI : 10.1103/PhysRevA.90.052119
Accès au bibtex
https://arxiv.org/pdf/1409.5388 BibTex

2013

Journal articles

titre
The logical clarinet: numerical optimization of the geometry of woodwind instruments.
auteur
Daniel Noreland, Jean Kergomard, Franck Laloë, Christophe Vergez, Philippe Guillemain, Alexis Guilloteau
article
Acta Acustica united with Acustica, 2013, 99, pp.615-628. ⟨10.3813/AAA.918641⟩
resume
The tone hole geometry of a clarinet is optimized numerically. The instrument is modeled as a network of one dimensional transmission line elements. For each (non-fork) fingering, we first calculate the resonance frequencies of the input impedance peaks, and compare them with the frequencies of a mathematically even chromatic scale (equal temperament). A least square algorithm is then used to minimize the differences and to derive the geometry of the instrument. Various situations are studied, with and without dedicated register hole and/or enlargement of the bore. With a dedicated register hole, the differences can remain less than 10 musical cents throughout the whole usual range of a clarinet. The positions, diameters and lengths of the chimneys vary regularly over the whole length of the instrument, in contrast with usual clarinets. Nevertheless, we recover one usual feature of instruments, namely that gradually larger tone holes occur when the distance to the reed increases. A fully chromatic prototype instrument has been built to check these calculations, and tested experimentally with an artificial blowing machine, providing good agreement with the numerical predictions.
DOI
DOI : 10.3813/AAA.918641
Accès au texte intégral et bibtex
https://hal.science/hal-00683477/file/clarinette-logique-12.pdf BibTex

Preprints, Working Papers, ...

titre
Angular momentum conservation in measurements on spin Bose-Einstein condensates
auteur
F. Laloë, W. J. Mullin
article
2013
resume
We discuss a thought experiment where two operators, Alice and Bob, perform transverse spin measurements on a quantum system; this system is initially in a double Fock spin state, which extends over a large distance in space so that the two operators are far away from each other. Standard quantum mechanics predicts that, when Alice makes a few measurements, a large transverse component of the spin angular momentum may appear in Bob's laboratory. A paradox then arises since local angular momentum conservation seems to be violated. It has been suggested that this angular momentum may be provided by the interaction with the measurement apparatuses. We show that this solution of the paradox is not appropriate, so that another explanation must be sought. The general question is the retroaction of a quantum system onto a measurement apparatus. For instance, when the measured system is entangled with another quantum system, can its reaction on a measurement apparatus be completely changed? Is angular momentum conserved only on average over several measurements, but not during one realization of the experiment?
Accès au bibtex
https://arxiv.org/pdf/1308.0739 BibTex

2011

Preprints, Working Papers, ...

titre
Amplitude control of quantum interference
auteur
W. J. Mullin, F. Laloë
article
2011
resume
Usually, the oscillations of interference effects are controlled by relative phases. We show that varying the amplitudes of quantum waves, for instance by changing the reflectivity of beam splitters, can also lead to quantum oscillations and even to Bell violations of local realism. We first study theoretically a generalization of the Hong-Ou-Mandel experiment to arbitrary source numbers and beam splitter transmittivity. We then consider a Bell type experiment with two independent sources, and find strong violations of local realism for arbitrarily large source number $N$; for small $N$, one operator measures essentially the relative phase of the sources and the other their intensities. Since, experimentally, one can measure the parity of the number of atoms in an optical lattice more easily than the number itself, we assume that the detectors measure parity.
Accès au bibtex
https://arxiv.org/pdf/1107.2883 BibTex
titre
NOON-state formation from Fock-state Bose-Einstein condensates
auteur
H. Cable, F. Laloë, W. J. Mullin
article
2011
resume
NOON states (states of the form $|N>_{a}|0>_{b}+|0>_{a}|N>_{b}$ where $a$ and $b$ are single particle states) have been used for predicting violations of local realism (Greenberger-Horne-Zeilinger violations) and are valuable in metrology for precision measurements of phase at the Heisenberg limit. We show theoretically how the use of two Fock state Bose-Einstein condensates as sources in a modified Mach-Zehnder interferometer can lead to the creation of the NOON state in which $a$ and $b$ refer to arms of the interferometer and $N$ is a subset of the total number of particles in the two condensates. The modification of the interferometer involves making {}"side" measurements of a few particles near the sources. These measurements put the remaining particles in a superposition of two phase states, which are converted into NOON states by a beam splitter if the phase states are orthogonal. When they are not orthogonal, a {}"feedforward" correction circuit is shown to convert them into proper form so a NOON results. We apply the NOON to the measurement of phase. Here the NOON experiment is equivalent to one in which a large molecule passes through two slits. The NOON components can be recombined in a final beam splitter to show interference.
Accès au bibtex
https://arxiv.org/pdf/1103.2304 BibTex

2010

Journal articles

titre
Iterated maps for clarinet-like systems
auteur
P.-A. Taillard, J. Kergomard, F. Laloë
article
Nonlinear Dynamics, 2010, 62 (1-2), pp.253-271. ⟨10.1007/s11071-010-9715-5⟩
resume
The dynamical equations of clarinet-like systems are known to be reducible to a non-linear iterated map within reasonable approximations. This leads to time oscillations that are represented by square signals, analogous to the Raman regime for string instruments. In this article, we study in more detail the properties of the corresponding non-linear iterations, with emphasis on the geometrical constructions that can be used to classify the various solutions (for instance with or without reed beating) as well as on the periodicity windows that occur within the chaotic region. In particular, we find a regime where period tripling occurs and examine the conditions for intermittency. We also show that, while the direct observation of the iteration function does not reveal much on the oscillation regime of the instrument, the graph of the high order iterates directly gives visible information on the oscillation regime (characterization of the number of period doubligs, chaotic behaviour, etc.).
DOI
DOI : 10.1007/s11071-010-9715-5
Accès au texte intégral et bibtex
https://hal.science/hal-00589493/file/PEER_stage2_10.1007%252Fs11071-010-9715-5.pdf BibTex
titre
Iterated maps for clarinet-like systems
auteur
Pierre-André Taillard, Jean Kergomard, Franck Laloë
article
Nonlinear Dynamics, 2010, 62, pp.253-271. ⟨10.1007/s11071-010-9715-5⟩
resume
The dynamical equations of clarinet-like systems are known to be reducible to a non-linear iterated map within reasonable approximations. This leads to time oscillations that are represented by square signals, analogous to the Raman regime for string instruments. In this article, we study in more detail the properties of the corresponding non-linear iterations, with emphasis on the geometrical constructions that can be used to classify the various solutions (for instance with or without reed beating) as well as on the periodicity windows that occur within the chaotic region. In particular, we find a regime where period tripling occurs and examine the conditions for intermittency. We also show that, while the direct observation of the iteration function does not reveal much on the oscillation regime of the instrument, the graph of the high order iterates directly gives visible information on the oscillation regime (characterization of the number of period doubligs, chaotic behaviour, etc.).
DOI
DOI : 10.1007/s11071-010-9715-5
Accès au texte intégral et bibtex
https://hal.science/hal-00440847/file/FLPATK_HAL2.pdf BibTex
titre
Beyond spontaneously broken symmetry in Bose-Einstein condensates
auteur
W. J. Mullin, F. Laloë
article
Physical Review Letters, 2010, 104, pp.150401. ⟨10.1103/PhysRevLett.104.150401⟩
resume
Spontaneous symmetry breaking (SSB) for Bose-Einstein condensates cannot treat phase off-diagonal effects, and thus not explain Bell inequality violations. We describe another situation that is beyond a SSB treatment: an experiment where particles from two (possibly macroscopic) condensate sources are used for conjugate measurements of the relative phase and populations. Off-diagonal phase effects are characterized by a "quantum angle" and observed via "population oscillations", signaling quantum interference of macroscopically distinct states (QIMDS).
DOI
DOI : 10.1103/PhysRevLett.104.150401
Accès au bibtex
https://arxiv.org/pdf/0912.5360 BibTex
titre
Spin Self-Rephasing and Very Long Coherence Times in a Trapped Atomic Ensemble
auteur
Christian Deutsch, Fernando Ramírez-Martínez, Clément Lacroûte, Friedemann Reinhard, Tapio Schneider, Jean-Noël Fuchs, Frédéric Piéchon, F. Laloë, Jakob Reichel, Peter Rosenbusch
article
Physical Review Letters, 2010, 105, pp.20401. ⟨10.1103/PhysRevLett.105.020401⟩
resume
We perform Ramsey spectroscopy on the ground state of ultracold Rb87 atoms magnetically trapped on a chip in the Knudsen regime. Field inhomogeneities over the sample should limit the 1/e contrast decay time to about 3 s, while decay times of 58±12s are actually observed. We explain this surprising result by a spin self-rephasing mechanism induced by the identical spin rotation effect originating from particle indistinguishability. We propose a theory of this synchronization mechanism and obtain good agreement with the experimental observations. The effect is general and may appear in other physical systems.
DOI
DOI : 10.1103/PhysRevLett.105.020401
Accès au texte intégral et bibtex
https://hal.science/hal-03785887/file/PhysRevLett.105.020401.pdf BibTex

Conference papers

titre
Cartes itérées appliquées à un instrument de type clarinette
auteur
Pierre-André Taillard, Jean Kergomard, Franck Laloë, Sami Karkar
article
10ème Congrès Français d'Acoustique, Apr 2010, Lyon, France
resume
Mc Intyre et coll. (1983) ont montré que l'on peut ramener le calcul des oscillations d'une clarinette à une simple itération, dans un modèle où le résonateur est cylindrique avec des pertes indépendantes de la fréquence, et où l'anche est vue comme un ressort sans inertie. Pour cela on choisit le couple des ondes aller et retour comme variables de base, et le système peut se ramener à l'itération d'une fonction f(x) qui relie les amplitudes de ces ondes, conduisant à des oscillations en signaux carrés. Nous donnons une étude plus approfondie de cette fonction et en déduisons un encadrement des valeurs des paramètres d'excitation pour lesquelles l'anche peut battre, ou encore pour lesquelles le signe du débit peut s'inverser. Les fonctions itérées de la fonction f(x) renseignent notamment sur la stabilité des régimes périodiques, ou aident à comprendre l'existence de régimes chaotiques, de fenêtres de périodicité ou d'intermittences. Enfin l'influence du paramètre de pertes sur la nature des principales bifurcations est étudiée.
Accès au texte intégral et bibtex
https://hal.science/hal-00537191/file/000088.pdf BibTex

Preprints, Working Papers, ...

titre
Creation of NOON states by double Fock-state/Bose-Einstein condensates
auteur
W. Mullin, Franck Laloë
article
2010
resume
NOON states (states of the form $|N>_{a}|0>_{b}+|0>_{a}|N>_{b}$ where $a$ and $b$ are single particle states) have been used for predicting violations of hidden-variable theories (Greenberger-Horne-Zeilinger violations) and are valuable in metrology for precision measurements of phase at the Heisenberg limit. We show theoretically how the use of two Fock state/Bose-Einstein condensates as sources in a modified Mach Zender interferometer can lead to the creation of the NOON state in which $a$ and $b$ refer to arms of the interferometer and $N$ is the total number of particles in the two condensates. The modification of the interferometer involves making conditional ``side'' measurements of a few particles near the sources. These measurements put the remaining particles in a superposition of two phase states, which are converted into NOON states by a beam splitter. The result is equivalent to the quantum experiment in which a large molecule passes through two slits. The NOON states are combined in a final beam splitter and show interference. Attempts to detect through which ``slit'' the condensates passed destroys the interference.
Accès au bibtex
https://arxiv.org/pdf/1006.3038 BibTex
titre
Quantum properties of a single beam splitter
auteur
F. Laloë, W. J. Mullin
article
2010
resume
When a single beam-splitter receives two beams of bosons described by Fock states (Bose-Einstein condensates at very low temperatures), interesting generalizations of the two-photon Hong-Ou-Mandel effect take place for larger number of particles. The distributions of particles at two detectors behind the beam splitter can be understood as resulting from the combination of two effects, the spontaneous phase appearing during quantum measurement, and the quantum angle. The latter introduces quantum "population oscillations", which can be seen as a generalized Hong-Ou-Mandel effect, although they do not always correspond to even-odd oscillations.
Accès au bibtex
https://arxiv.org/pdf/1004.1731 BibTex
titre
Spin self-rephasing and very long coherence times in a trapped atomic ensemble
auteur
Christian Deutsch, Fernando Ramirez-Martinez, Clement Lacroûte, Friedemann Reinhard, Tobias Schneider, Jean-Noël Fuchs, Frédéric Piéchon, Franck Laloë, Jakob Reichel, Peter Rosenbusch
article
2010
resume
We perform Ramsey spectroscopy on the ground state of ultra-cold 87Rb atoms magnetically trapped on a chip in the Knudsen regime. Field inhomogeneities over the sample should limit the 1/e contrast decay time to about 3 s. Nevertheless, decay times of 58 s are actually observed. We explain this surprising result by a spin self-rephasing mechanism induced by the identical spin rotation effect originating from particle indistinguishability. We propose a theory of this synchronization mechanism and obtain good agreement with the experimental observations. The effect is general and susceptible to appear in other physical systems.
Accès au bibtex
https://arxiv.org/pdf/1003.5925 BibTex

2009

Journal articles

titre
Fringe free holographic measurements of large amplitude vibrations
auteur
Fadwa Joud, Frédéric Verpillat, Franck Laloë, Atlan Michael, Jean Hare, Michel Gross
article
Optics Letters, 2009, 34 (23), pp.3698
resume
In the measurement of the amplitude of vibration of objects, holographic imaging techniques usually involve fringe counting; due to the limited resolution of images, measurements of large amplitudes are not accessible. We demonstrate a technique that suppresses the necessity of fringe counting: frequency sideband imaging, where the order of the sideband is considered as a marker of the amplitude. The measurement is completely local: no comparison with another reference point on the object is necessary. It involves a sharp variation of a signal, which makes it robust against perturbations. The method is demonstrated in an experiment made with a vibrating clarinet reed; phase modulations as large as $1000$ radians have been measured.
Accès au texte intégral et bibtex
https://hal.science/hal-00468198/file/anche-unwrapping_revised-FL.pdf BibTex
titre
Imaging of a vibrating object by Sideband Digital Holography
auteur
Fadwa Joud, Franck Laloë, Michael Atlan, Jean Hare, Michel Gross
article
Optics Express, 2009, 17 (4), pp.2774-2779. ⟨10.1364/OE.17.002774⟩
resume
We obtain quantitative measurements of the oscillation amplitude of vibrating objects by using sideband digital holography. The frequency sidebands on the light scattered by the object, shifted by n times the vibration frequency, are selectively detected by heterodyne holography, and images of the object are calculated for different orders n. Orders up to n=120 have been observed, allowing the measurement of amplitudes of oscillation that are significantly larger than the optical wavelength. Using the positions of the zeros of intensity for each value of n, we reconstruct the shape of vibration the object.
DOI
DOI : 10.1364/OE.17.002774
Accès au texte intégral et bibtex
https://hal.science/hal-00321050/file/grossSDH-FL_.pdf BibTex
titre
Large amplitude spin oscillations in a collisionless trapped atomic gas
auteur
F. Piechon, J. N. Fuchs, F. Laloë
article
Physical Review Letters, 2009, 102, pp.215301
resume
We propose an explanation of the recently observed strong spin segregation in a trapped Fermi gas by Du et al. Numerical and analytical solutions of a spin 1/2 kinetic equation in a collisionless regime explain quantitatively the observation of an "anomalous" large time scale and amplitude of the segregation. The key difference with previous experiment on bosons rests more in the diluteness of the gas than in the quantum statistics of the atoms. When they undergo fast ballistic oscillations in the trap, they average the inhomogeneous external field in an energy dependent way, so that their transverse spin precession frequency becomes proportional to their energy. Interactions between atoms of different energies and different spin directions then involve the identical spin rotation effect (ISRE), which transfers atoms to the up or down spin state in an energy dependent way. Since low energy atoms are closer to the center of the trap than high energy atoms, which can visit its edges, the final outcome is a strong correlation between spins and positions.
Accès au bibtex
https://arxiv.org/pdf/0901.4008 BibTex
titre
Interferometry with independent Bose-Einstein ondensates: parity as an EPR/Bell quantum variable
auteur
Franck Laloë, William J. Mullin
article
The European Physical Journal B: Condensed Matter and Complex Systems, 2009, 70, pp.377-396
resume
When independent Bose-Einstein condensates (BEC), described quantum mechanically by Fock (number) states, are sent into interferometers, the measurement of the output port at which the particles are detected provides a binary measurement, with two possible results $\pm1$. With two interferometers and two BEC's, the parity (product of all results obtained at each interferometer) has all the features of an Einstein-Podolsky-Rosen quantity, with perfect correlations predicted by quantum mechanics when the settings (phase shifts of the interferometers) are the same.\ When they are different, significant violations of Bell inequalities are obtained.\ These violations do not tend to zero when the number $N$ of particles increases, and can therefore be obtained with arbitrarily large systems, but a condition is that all particles should be detected. We discuss the general experimental requirements for observing such effects, the necessary detection of all particles in correlation, the role of the pixels of the CCD detectors, and that of the alignments of the interferometers in terms of matching of the wave fronts of the sources in the detection regions. Another scheme involving three interferometers and three BEC's is discussed; it leads to Greenberger Horne Zeilinger (GHZ) sign contradictions, as in the usual GHZ\ case with three particles, but for an arbitrarily large number of them.\ Finally, generalizations of the Hardy impossibilities to an arbitrarily large number of particles are introduced. BEC's provide a large versality for observing violations of local realism in a variety of experimental arrangements.
Accès au texte intégral et bibtex
https://hal.science/hal-00345342/file/parity.pdf BibTex

Preprints, Working Papers, ...

titre
Classical phases and quantum angles in the description of interfering Bose-Einstein condensates
auteur
W. J. Mullin, F. Laloë
article
2009
resume
The interference of two Bose-Einstein condensates, initially in Fock states, can be described in terms of their relative phase, treated as a random unknown variable. This phase can be understood, either as emerging from the measurements, or preexisting to them; in the latter case, the originating states could be phase states with unknown phases, so that an average over all their possible values is taken. Both points of view lead to a description of probabilities of results of experiments in terms of a phase angle, which plays the role of a classical variable. Nevertheless, in some situations, this description is not sufficient: another variable, which we call the "quantum angle", emerges from the theory. This article studies various manifestations of the quantum angle. We first introduce the quantum angle by expressing two Fock states crossing a beam splitter in terms of phase states, and relate the quantum angle to off-diagonal matrix elements in the phase representation. Then we consider an experiment with two beam splitters, where two experimenters make dichotomic measurements with two interferometers and detectors that are far apart; the results lead to violations of the Bell-Clauser-Horne-Shimony-Holt inequality (valid for local-realistic theories, including classical descriptions of the phase). Finally, we discuss an experiment where particles from each of two sources are either deviated via a beam splitter to a side collector or proceed to the point of interference. For a given interference result, we find "population oscillations" in the distributions of the deviated particles, which are entirely controlled by the quantum angle. Various versions of population oscillation experiments are discussed, with two or three independent condensates.
Accès au bibtex
https://arxiv.org/pdf/0908.3012 BibTex

2008

Journal articles

titre
Interference of Bose-Einstein condensates: quantum non-local effects
auteur
William J. Mullin, Franck Laloë
article
Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2008, A78, pp.061605. ⟨10.1103/PhysRevA.78.061605⟩
resume
Quantum systems in Fock states do not have a phase. When two or more Bose-Einstein condensates are sent into interferometers, they nevertheless acquire a relative phase under the effect of quantum measurements. The usual explanation relies on spontaneous symmetry breaking, where phases are ascribed to all condensates and treated as unknown classical quantities. However, this image is not always sufficient: when all particles are measured, quantum mechanics predicts probabilities that are sometimes in contradiction with it, as illustrated by quantum violations of local realism. In this letter, we show that interferometers can be used to demonstrate a large variety of violations with an arbitrarily large number of particles. With two independent condensates, we find violations of the BCHSH inequalities, as well as new N-body Hardy impossibilities. With three condensates, we obtain new GHZ (Greenberger, Horne and Zeilinger) type contradictions.
DOI
DOI : 10.1103/PhysRevA.78.061605
Accès au texte intégral et bibtex
https://hal.science/hal-00276743/file/Interf-Letter-2-columns.pdf BibTex
titre
EPR argument and Bell inequalities for Bose-Einstein spin condensates
auteur
Franck Laloë, William J. Mullin
article
Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2008, 77, pp.022108. ⟨10.1103/PhysRevA.77.022108⟩
resume
We discuss the properties of two Bose-Einstein condensates in different spin states, represented quantum mechanically by a double Fock state. Individual measurements of the spins of the particles are performed in transverse directions (perpendicular to the spin quantization axis), giving access to the relative phase of the two macroscopically occupied states. Before the first spin measurement, the phase is completely undetermined; after a few measurements, a more and more precise knowledge of its value emerges under the effect of the quantum measurement process. This naturally leads to the usual notion of a quasi-classical phase (Anderson phase) and to an interesting transposition of the EPR (Einstein-Podolsky-Rosen) argument to macroscopic physical quantities. The purpose of this article is to discuss this transposition, as well as situations where the notion of a quasi-classical phase is no longer sufficient to account for the quantum results, and where significant violations of Bell type inequalities are predicted.
DOI
DOI : 10.1103/PhysRevA.77.022108
Accès au texte intégral et bibtex
https://hal.science/hal-00189827/file/Big-Bell-Bec.pdf BibTex

2007

Journal articles

titre
Quantum non-local effects with Bose-Einstein condensates
auteur
Franck Laloë, William J. Mullin
article
Physical Review Letters, 2007, 99, pp.150401
resume
We study theoretically the properties of two Bose-Einstein condensates in different spin states, represented by a double Fock state. Individual measurements of the spins of the particles are performed in transverse directions, giving access to the relative phase of the condensates. Initially, this phase is completely undefined, and the first measurements provide random results. But a fixed value of this phase rapidly emerges under the effect of the successive quantum measurements, giving rise to a quasi-classical situation where all spins have parallel transverse orientations. If the number of measurements reaches its maximum (the number of particles), quantum effects show up again, giving rise to violations of Bell type inequalities. The violation of BCHSH inequalities with an arbitrarily large number of spins may be comparable (or even equal) to that obtained with two spins.
Accès au texte intégral et bibtex
https://hal.science/hal-00139664/file/Bec-Bell-PRL-final.pdf BibTex
titre
The Kosterlitz-Thouless-Berezinskii transition of homogeneous and trapped Bose gases in two dimensions
auteur
Markus Holzmann, Gordon Baym, Jean-Paul Blaizot, Franck Laloë
article
Proceedings of the National Academy of Sciences of the United States of America, 2007, 104, pp.1476
resume
We derive the scaling structure of the Kosterlitz-Thouless-Berezinskii (KTB) transition temperature of a homogeneous Bose gas in two dimensions within diagrammatic perturbation theory. Approaching the system from above the transition, we calculate the critical temperature, $T_{KT}$, and show how the superfluid mass density emerges from Josephson's relation as an interplay between the condensate density in a finite size system, and the infrared structure of the single particle Green's function. We then discuss the trapped two-dimensional Bose gas, where the interaction changes the transition qualitatively from Bose-Einstein in an ideal gas to a KTB transition in the thermodynamic limit. We show that the transition temperature lies below the ideal Bose-Einstein transition temperature, and calculate the first correction in terms of the interparticle interactions. The jump of the total superfluid mass at the transition is suppressed in a trapped system.
Accès au bibtex
https://arxiv.org/pdf/cond-mat/0508131 BibTex

Book sections

titre
Bose-Einstein condensates and quantum non-locality
auteur
Franck Laloë
article
Theo M. Nieuwenhuizen et al. Beyond the quantum, World Scientific, pp.35, 2007, colloque tenu à Leyde en mai 2006
resume
The EPR argument points to the existence of additional variables that are necessary to complete standard quantum theory. It was dismissed by Bohr because it attributes physical reality to isolated microscopic systems, independently of the macroscopic measurement apparatus. Here, we transpose the EPR argument to macroscopic systems, assuming that they are in spatially extended Fock spin states and subject to spin measurements in remote regions of space. Bohr's refutation of the EPR argument does not seem to apply in this case, since the difference of scale between the microscopic measured system and the macroscopic measuring apparatus can no longer be invoked.
Accès au texte intégral et bibtex
https://hal.science/hal-00110808/file/BEC-EPR.pdf BibTex

2006

Journal articles

titre
The evolution of additional (hidden) quantum variables in the interference of Bose-Einstein condensates
auteur
W. J. Mullin, R. Krotkov, F. Laloë
article
Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2006, 74, pp.023610. ⟨10.1103/PhysRevA.74.023610⟩
resume
Additional variables (also often called ``hidden variables'') are sometimes added to standard quantum mechanics in order to remove its indeterminism or ``incompletness,'' and to make the measurement process look more classical. Here we discuss a case in which an additional variable arises almost spontaneously from the quantum formalism: the emergence of relative phase between two highly populated Fock state Bose-Einstein condensates. The model simulated here involves the interference of two Bose condensates, one with all up spins, and the other with down spins, along a z-axis. With the clouds overlapping, we consider the results of measuring spins in a transverse plane (the general direction is studied in an appendix). The determination of the previously ``hidden'' phase becomes progressively more definite as additional measurements are made. We also provide an analysis of a recent and closely related experiment.
DOI
DOI : 10.1103/PhysRevA.74.023610
Accès au bibtex
https://arxiv.org/pdf/cond-mat/0605038 BibTex

Lectures

titre
Cours de DEA sur les symétries
auteur
Franck Laloë
article
DEA. 2006
resume
Notes de cours de DEA sur les symétries et principalement sur les groupes continues (368 pages).
Accès au texte intégral et bibtex
https://cel.hal.science/cel-00092953/file/chapitres.pdf BibTex

2005

Journal articles

titre
Analysis and optimisation of the tuning of the twelfths for a clarinet resonator
auteur
Vincent Debut, Jean Kergomard, Franck Laloë
article
Applied Acoustics, 2005, 66, pp.365-409
resume
Even if the tuning between the first and second register of a clarinet has been optimized by instrument makers, the lowest twelfths remain slightly too large (inharmonicity). In this article, we study the problem from two different points of view. First, we systematically review various physical reasons why this inharmonicity may take place, and the effect of different bore perturbations inserted in cylindrical instruments. Applications to a real clarinet resonator and comparisons with impedance measurements are then presented. A commonly accepted idea is that the register hole is the dominant cause for this inharmonicity: it is natural to expect that opening this hole will raise the resonance frequencies of the instrument, except for the note for which the hole is at the pressure node. We show that the real situation is actually more complicated because other effects, such as open holes or bore taper and bell, introduce resonance shifts that are comparable but with opposite sign, so that a relatively good overall compensation takes place. The origin of the observed inharmonicity in playing frequencies is therefore different. In a second part, we use an elementary model of the clarinet in order to isolate the effect of the register hole: a perfect cylindrical tube without closed holes. Optimization techniques are then used to calculate an optimum location for the register hole; the result turns out to be close to the location chosen by clarinet makers. Finally, attempts are made numerically to improve the situation by introducing small perturbations in the higher part of the cylindrical resonator, but no satisfactory improvement is obtained.
Accès au texte intégral et bibtex
https://hal.science/hal-00000589/file/applied_last_version_fig.pdf BibTex
titre
Long-lived quantum memory with nuclear atomic spins
auteur
Aurelien Dantan, Gael Reinaudi, Alice Sinatra, Franck Laloë, Elisabeth Giacobino, Michel Pinard
article
Physical Review Letters, 2005, 95, pp.123002. ⟨10.1103/PhysRevLett.95.123002⟩
resume
We propose to store non-classical states of light into the macroscopic collective nuclear spin ($10^{18}$ atoms) of a $^3$He vapor, using metastability exchange collisions. These collisions, commonly used to transfer orientation from the metastable state $2^{3}S_1$ to the ground state state of $^3$He, can also transfer quantum correlations. This gives a possible experimental scheme to map a squeezed vacuum field state onto a nuclear spin state with very long storage times (hours).
DOI
DOI : 10.1103/PhysRevLett.95.123002
Accès au texte intégral et bibtex
https://hal.science/hal-00004764/file/der.pdf BibTex
titre
The hidden phase of Fock states; quantum non-local effects
auteur
Franck Laloë
article
The European Physical Journal D : Atomic, molecular, optical and plasma physics, 2005, 33, pp.87-97. ⟨10.1140/epjd/e2005-00014-0⟩
resume
We revisit the question of how a definite phase between Bose-Einstein condensates can spontaneously appear under the effect of measurements. We first consider a system that is the juxtaposition of two subsystems in Fock states with high populations, and assume that successive individual position measurements are performed. Initially, the relative phase is totally undefined, and no interference effect takes place in the first position measurement. But, while successive measurements are accumulated, the relative phase becomes better and better known, and a clear interference pattern emerges. It turns out that all observed results can be interpreted in terms of a pre-existing, but totally unknown, relative phase, which remains exactly constant during the experiment. We then generalize the results to more condensates. We also consider other initial quantum states than pure Fock states, and distinguish between intrinsic phase of a quantum state and phase induced by measurements. Finally, we examine the case of multiple condensates of spin states. We discuss a curious quantum effect, where the measurement of the spin angular momentum of a small number of particles can induce a big angular momentum in a much larger assembly of particles, even at an arbitrary distance. This spin observable can be macroscopic, assimilable to the pointer of a measurement apparatus, which illustrates the non-locality of quantum mechanics with particular clarity.
DOI
DOI : 10.1140/epjd/e2005-00014-0
Accès au texte intégral et bibtex
https://hal.science/hal-00002753/file/phase.pdf BibTex

Book sections

titre
La condensation de Bose-Einstein dans les gaz
auteur
Claude Cohen-Tannoudji, Jean Dalibard, Franck Laloë
article
Einstein aujourd'hui, EDP Sciences et CNRS Editions, pp.87-127, 2005
Accès au bibtex
BibTex

2004

Journal articles

titre
Bose-Einstein transition temperature in a dilute repulsive gas
auteur
Markus Holzmann, Jean-Noël Fuchs, Gordon Baym, Jean-Paul Blaizot, Franck Laloë
article
Comptes Rendus. Physique, 2004, 5, pp.21. ⟨10.1016/j.crhy.2004.01.003⟩
resume
We discuss certain specific features of the calculation of the critical temperature of a dilute repulsive Bose gas. Interactions modify the critical temperature in two different ways. First, for gases in traps, temperature shifts are introduced by a change of the density profile, arising itself from a modification of the equation of state of the gas (reduced compressibility); these shifts can be calculated simply within mean field theory. Second, even in the absence of a trapping potential (homogeneous gas in a box), temperature shifts are introduced by the interactions; they arise from the correlations introduced in the gas, and thus lie inherently beyond mean field theory - in fact, their evaluation requires more elaborate, non-perturbative, calculations. One illustration of this non-perturbative character is provided by the solution of self-consistent equations, which relate together non-linearly the various energy shifts of the single particle levels k. These equations predict that repulsive interactions shift the critical temperature (at constant density) by an amount which is positive, and simply proportional to the scattering length a; nevertheless, the numerical coefficient is difficult to compute. Physically, the increase of the temperature can be interpreted in terms of the reduced density fluctuations introduced by the repulsive interactions, which facilitate the propagation of large exchange cycles across the sample.
DOI
DOI : 10.1016/j.crhy.2004.01.003
Accès au texte intégral et bibtex
https://hal.science/hal-00000770/file/comm-bec.pdf BibTex

2003

Journal articles

titre
Large amplitude spin waves in ultra-cold gases
auteur
Jean-Noël Fuchs, Dimitri M. Gangardt, Franck Laloë
article
The European Physical Journal D : Atomic, molecular, optical and plasma physics, 2003, 25, pp.57
resume
We discuss the theory of spin waves in non-degenerate ultra-cold gases, and compare various methods which can be used to obtain appropriate kinetic equations. We then study non-hydrodynamic situations, where the amplitude of spin waves is sufficiently large to bring the system far from local equilibrium. In the first part of the article, we compare two general methods which can be used to derive a kinetic equation for a dilute gas of atoms (bosons orfermions) with two internal states (treated as a pseudo-spin 1/2). The collisional methods are in the spirit of Boltzmann's original derivation of his kinetic equation where, at each point of space, the effects of all sorts of possible binary collisions are added. We discuss two different versions of collisional methods, the Yvon-Snider approach and the S matrixapproach. The second method uses the notion of mean field, which modifies the drift term of the kinetic equation, in the line of the Landau theory oftransport in quantum liquids. For a dilute cold gas, it turns out that all these derivations lead to the same drift terms in the transport equation, but differ in the precise expression of the collision integral and in higher order gradient terms.In the second part of the article, the kinetic equation is applied to spin waves in trapped ultra-cold gases. Numerical simulations are used to illustrate the strongly non-hydrodynamic character of the spin waves recently observed with trapped Rb87 atoms. The decay of the phenomenon, which takes place when the system relaxes back towards equilibrium, is also discussed, with a short comment on decoherence.
Accès au texte intégral et bibtex
https://hal.science/hal-00000306/file/bigisre.pdf BibTex

2002

Journal articles

titre
Internal state conversion of ultracold gases
auteur
Jean-Noël Fuchs, Dimitri M. Gangardt, Franck Laloë
article
Physical Review Letters, 2002, 88, pp.230404
resume
We consider an ultracold gas of (non-condensed) bosons or fermions with twointernal states, and study the effect of a gradient of the transitionfrequency between these states. When a $\\\\pi/2$ RF pulse is applied to thesample, exchange effects during collisions transfer the atoms into internal stateswhich depend on the direction of their velocity. This results, after a shorttime, in a spatial separation between the two states. A kinetic equation issolved analytically and numerically; the results agree well with the recentobservations of Lewandowski et al.
Accès au bibtex
https://arxiv.org/pdf/cond-mat/0112228 BibTex
titre
Ursell operators in statistical physics of dense systems: the role of high order operators and of exchange cycles
auteur
Jean-Noël Fuchs, Markus Holzmann, Franck Laloë
article
The European Physical Journal B: Condensed Matter and Complex Systems, 2002, 25, pp.463
resume
The purpose of this article is to discuss cluster expansions in dense quantum systems, as well as their interconnection with exchange cycles. We show in general how the Ursell operators of order $l\geq3$ contribute to an exponential which corresponds to a mean-field energy involving the second operator $U_{2}$, instead of the potential itself as usual - in other words,the mean-field correction is expressed in terms of a modification of a local Boltzmann equilibrium. In a first part, we consider classical statistical mechanics and recall the relation between the reducible part of the classical cluster integrals and the mean-field; we introduce an alternative method to obtain the linear density contribution to the mean-field, which is based on the notion of tree-diagrams and provides a preview of the subsequent quantum calculations. We then proceed to study quantum particles with Boltzmann statistics (distinguishable particles) and show that each Ursell operator $U_{n}$ with $n\geq3$ contains a "tree-reducible part'', which groups naturally with $U_{2}$ through a linear chain of binary interactions; this part contributes to the associated mean-field experienced by particles in the fluid. The irreducible part, on the other hand, corresponds to the effects associated with three (or more) particles interacting all together at the same time. We then show that the same algebra holds in the case of Fermi or Bose particles, and discuss physically the role of the exchange cycles, combined with interactions. Bose condensed systems are not considered at this stage. The similarities and differences between Boltzmann and quantum statistics are illustrated by this approach, in contrast with field theoretical or Green's functions methods, which do not allow a separate study of the role of quantum statistics and dynamics.
Accès au bibtex
https://arxiv.org/pdf/cond-mat/0109265 BibTex

2001

Journal articles

titre
Do we really understand quantum mechanics?
auteur
Franck Laloë
article
American Journal of Physics, 2001, 69, pp.655 - 701. ⟨10.1119/1.1356698⟩
resume
This article presents a general discussion of several aspects of our present understanding of quantum mechanics. The emphasis is put on the very special correlations that this theory makes possible: they are forbidden by very general arguments based on realism and local causality. In fact, these correlations are completely impossible in any circumstance, except the very special situations designed by physicists especially to observe these purely quantum effects. Another general point that is emphasized is the necessity for the theory to predict the emergence of a single result in a single realization of an experiment. For this purpose, orthodox quantum mechanics introduces a special postulate: the reduction of the state vector, which comes in addition to the Schrödinger evolution postulate. Nevertheless, the presence in parallel of two evolution processes of the same object (the state vector) maybe a potential source for conflicts; various attitudes that are possible to avoid this problem are discussed in this text. After a brief historical introduction, recalling how the very special status of the state vector has emerged in quantum mechanics, various conceptual difficulties are introduced and discussed. The Einstein Podolsky Rosen (EPR) theorem is presented with the help of a botanical parable, in a way that emphasizes how deeply the EPR reasoning is rooted into what is often called "scientific method''. In another section the GHZ argument, the Hardy impossibilities, as well as the BKS theorem are introduced in simple terms.
DOI
DOI : 10.1119/1.1356698
Accès au texte intégral et bibtex
https://hal.science/hal-00000001/file/mq-anglais.pdf BibTex
titre
Bose-Einstein transition in a dilute interacting gas
auteur
Gordon Baym, Jean-Paul Blaizot, Markus Holzmann, Franck Laloë, Dominique Vautherin
article
The European Physical Journal B: Condensed Matter and Complex Systems, 2001, 24, pp.107-124
resume
We study the effects of repulsive interactions on the critical density for the Bose-Einstein transition in a homogeneous dilute gas of bosons. First, wepoint out that the simple mean field approximation produces no change in thecritical density, or critical temperature,and discuss the inadequacies ofvarious contradictory results in the literature. Then, both within theframeworks of Ursell operators and of Green's functions, we deriveself-consistent equations that include correlations in the systemand predict the change of the critical density. We argue that the dominantcontribution to this change can be obtained within classical field theory and show that the lowest order correction introduced by interactions is linear inthe scattering length, $a$, with a positive coefficient. Finally, wecalculate this coefficient within various approximations, and compare withvarious recent numerical estimates.
Accès au bibtex
https://arxiv.org/pdf/cond-mat/0107129 BibTex
titre
Nonanalytic dependence of the transition temperature of the homogeneous dilute gas on scattering length
auteur
Markus Holzmann, Gordon Baym, Jean-Paul Blaizot, Franck Laloë
article
Physical Review Letters, 2001, 87, pp.120403. ⟨10.1103/PhysRevLett.87.120403⟩
resume
We show that the shift in the transition temperature ofthe dilute homogeneous Bose gas is non-analytic in the scattering amplitude,$a$. The first correction beyond the positive linear shift in $a$ is negativeand of order $a^2\\ln a$. This non-universal non-analytic structure indicateshow the discrepancies between numerical calculations at finite $a$ can bereconciled with calculations of the limit $a \\to0$, since the linearity isapparent only for anomalously small $a$.
DOI
DOI : 10.1103/PhysRevLett.87.120403
Accès au bibtex
https://arxiv.org/pdf/cond-mat/0103595 BibTex

2000

Journal articles

titre
Bogolubov transformation for distinguishable particles
auteur
Markus Holzmann, Franck Laloë
article
Moroccan Journal of Statistical Physics, 2000, 3, pp.1
resume
The Bogoliubov transformation is generally derived in the context of identical bosons with the use of "second quantized'' $a$ and $a^{\dagger}$ operators (or, equivalently, in field theory). Here, we show that the transformation, together with its characteristic energy spectrum, can also be derived within the Hilbert space of distinguishable particles, obeying Boltzmann statistics; in this derivation, ordinary dyadic operators play the role usually played by the $a$ and $a^{\dagger}$ operators; therefore, breaking the symmetry of particle conservation is not necessary.
Accès au texte intégral et bibtex
https://hal.science/hal-00001408/file/bogoliubov.pdf BibTex
titre
Validity of the Hohenberg theorem for a generalized BEC in 2D
auteur
William J. Mullin, Markus Holzmann, Franck Laloë
article
Journal of Low Temperature Physics, 2000, 121, pp.263-268
resume
Several authors have considered the possibility of a generalized Bose-Einstein condensation (BEC) in which a band of low states is occupied so that the total occupation number is macroscopic, even if the occupation number of each state is not extensive. The Hohenberg theorem (HT) states that there is no BEC into a single state in 2D; we consider its validity for the case of a generalized condensation and find that, under certain conditions, the HT does {\em not} forbid a BEC in 2D. We discuss whether this situation actually occurs in any theoretical model system.
Accès au bibtex
https://arxiv.org/pdf/cond-mat/0009070 BibTex
titre
Instability in a dilute 2D interacting Bose system
auteur
William J. Mullin, Markus Holzmann, Franck Laloë
article
Journal of Low Temperature Physics, 2000, 121, pp.269-274
resume
The formalism of Ursell operators provides a self-consistent integral equation for the one-particle reduced operator. In three dimensions this technique yields values of the shift in the Bose-Einstein condensation (BEC) transition temperature, as a function of the scattering length, that are in good agreement with those of Green's function and quantum Monte Carlo methods. We have applied the same equations to a uniform two-dimensional system and find that, as we alter the chemical potential, an instability develops so that the self-consistent equations no longer have a solution. This instability, which seems to indicate that interactions restore a transition, occurs at a non-zero value of an effective chemical potential. The non-linear equations are limited to temperatures greater than or equal to Tc, so that they do not indicate the nature of the new stable state, but we speculate concerning whether it is a Kosterlitz-Thouless state or a ``smeared'' BEC, which might avoid any violation of the Hohenberg theorem, as described in an accompanying paper.
Accès au bibtex
https://arxiv.org/pdf/cond-mat/0009071 BibTex

Books

titre
Qvantovaja Mechanika
auteur
Claude Cohen-Tannoudji, Bernard Diu, Franck Laloë
article
Izd. Ural. Univ., pp.942 + 799, 2000
Accès au bibtex
BibTex

1999

Journal articles

titre
The transition temperature of the dilute interacting Bose gas
auteur
Gordon Baym, Jean-Paul Blaizot, Markus Holzmann, Dominique Vautherin, Franck Laloë
article
Physical Review Letters, 1999, 83, pp.1703-1706. ⟨10.1103/PhysRevLett.83.1703⟩
resume
We show that the critical temperature of a uniform dilute Bose gas increases linearly with the s-wave scattering length describing the repulsion between the particles. Because of infrared divergences, the magnitude of the shift cannot be obtained from perturbation theory, even in the weak coupling regime; rather, it is proportional to the size of the critical region in momentum space. By means of a self-consistent calculation of the quasiparticle spectrum at low momenta at the transition, we find an estimate of the effect in reasonable agreement with numerical simulations.
DOI
DOI : 10.1103/PhysRevLett.83.1703
Accès au bibtex
https://arxiv.org/pdf/cond-mat/9905430 BibTex
titre
Bose-Einstein condensation in interacting gases
auteur
Markus Holzmann, Peter Grüter, Franck Laloë
article
The European Physical Journal B: Condensed Matter and Complex Systems, 1999, 10, pp.739
resume
We study the occurrence of a Bose-Einstein transition in a dilute gas with repulsive interactions, starting from temperatures above the transition temperature. The formalism, based on the use of Ursell operators, allows us to evaluate the one-particle density operator with more flexibility than in mean-field theories, since it does not necessarily coincide with that of an ideal gas with adjustable parameters (chemical potential, etc.). In a first step, a simple approximation is used (Ursell-Dyson approximation), which allow us to recover results which are similar to those of the usual mean-field theories. In a second step, a more precise treatment of the correlations and velocity dependence of the populations in the system is elaborated. This introduces new physical effects, such as a change of the velocity profile just above the transition: the proportion of atoms with low velocities is higher than in an ideal gas. A consequence of this distortion is an increase of the critical temperature (at constant density) of the Bose gas, in agreement with those of recent path integral Monte-Carlo calculations for hard spheres.
Accès au bibtex
https://arxiv.org/pdf/cond-mat/9809356 BibTex

1997

Journal articles

titre
Critical Temperature of Bose-Einstein condensation of hard sphere gases
auteur
Franck Laloë, David M. Ceperley, Peter Grüter
article
Physical Review Letters, 1997, 79, pp.3549
resume
We determine the critical temperature of hard-sphere Bosons in a cubic box by path-integral Monte Carlo simulations and finite-size scaling. We obtain an enhancement compared to the ideal gas at low densities in the form of a power law in density with exponent $1/3$. At high densities the result for liquid helium, namely a lower critical temperature than in the non-interacting case, is recovered. We give a microscopic explanation for the observed behavior.
Accès au bibtex
https://arxiv.org/pdf/cond-mat/9707028 BibTex
titre
Oscillation threshold of woodwind instruments
auteur
Noël Grand, Joël Gilbert, Franck Laloë
article
Acta Acustica united with Acustica, 1997, 83, pp.137
resume
We give a theoretical study of the nature of the bifurcations occurring at the oscillation threshold of woodwind instruments, or of physical systems obeying similar non-linear equations of motion. We start from the simplest description of the acoustical behavior these instruments, a mathematical model containing two equations only, one of which is linear but includes delays, while the other is non-linear but has no delay, and discuss its predictions concerning the characteristics of the small oscillations. In particular we study the nature of the bifurcation occurring at threshold; if the bifurcation is direct, the amplitude of the oscillations increases progressively when the control parameter exceeds a threshold value; but, if the bifurcation is inverse, very small oscillations are not necessarily stable and the oscillation may jump discontinuously to a finite amplitude. While direct bifurcations correspond better to what naive intuition would expect, the surprising result of our calculations is their occurrence is by no means the general rule. We also discuss the shape (spectral content) of the small oscillations, and show that they do not always become quasisinusoidal in the limit of infinitely small solutions, in contrast with what is often assumed in the literature (Worman rule). Frequency shifts are investigated as well near threshold. More generally, we show how, despite of the simplicity of the equations of motion themselves, the characteristics of the non linearities of the excitator and of those of the resonator combine to produce a variety of possible behaviors which are not necessarily intuitive.
Accès au texte intégral et bibtex
https://hal.science/hal-00001412/file/acustica.pdf BibTex
titre
Oscillation threshold of woodwind instruments
auteur
Noël Grand, Joel Gilbert, Franck Laloë
article
Acta Acustica united with Acustica, 1997, 83, pp.137
Accès au bibtex
BibTex
titre
Ursell Operators in Statistical Physics III: Thermodynamic Properties of Degenerate Gases
auteur
P. Grüter, F. Laloë, A. Meyerovich, W. Mullin
article
Journal de Physique I, 1997, 7 (3), pp.485-508. ⟨10.1051/jp1:1997171⟩
resume
We study in more details the properties of the generalized Beth Uhlenbeck formula obtained in a preceding article. This formula leads to a simple integral expression of the grand potential of any dilute system, where the interaction potential appears only through the matrix elements of the second order Ursell operator U2. Our results remain valid for significant degree of degeneracy of the gas, but not when Bose Einstein (or BCS) condensation is reached, or even too close to this transition point. We apply them to the study of the thermodynamic properties of degenerate quantum gases: equation of state, magnetic susceptibility, effects of exchange between bound states and free particles, etc. We compare our predictions to those obtained within other approaches, especially the “pseudo potential” approximation, where the real potential is replaced by a potential with zero range (Dirac delta function). This comparison is conveniently made in terms of a temperature dependent quantity, the “Ursell length”, which we define in the text. This length plays a role which is analogous to the scattering length for pseudopotentials, but it is temperature dependent and may include more physical effects than just binary collision effects; for instance, for fermions at very low temperatures, it may change sign or increase almost exponentially. As an illustration, numerical results for quantum hard spheres are given.
DOI
DOI : 10.1051/jp1:1997171
Accès au texte intégral et bibtex
https://hal.science/jpa-00247339/file/ajp-jp1v7p485.pdf BibTex

Books

titre
Quantenmechanik
auteur
Claude Cohen-Tannoudji, Bernard Diu, Franck Laloë
article
Walter de Gruyter, pp.755+675, 1997
Accès au bibtex
BibTex

1995

Journal articles

titre
Spin dynamics in spin polarized Fermi gases
auteur
A.E. Meyerovich, S. Stepaniants, Franck Laloë
article
Journal of Low Temperature Physics, 1995, 101, pp.803
Accès au bibtex
BibTex
titre
Statistical Quasi Particles in Transverse Dynamics
auteur
A.E. Meyerovich, S. Stepaniants, Franck Laloë
article
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 1995, 52, pp.6808
resume
We analyze the validity of the Fermi-liquid approach to transverse dynamics of spin-polarized gases at arbitrary temperatures. We demonstrate that the diagrammatic kinetic equation for transverse processes can be formulated as a simpler, but completely equivalent equation in terms of ``statistical quasiparticles.'' The equation includes all coherent and dephasing molecular-field terms as well as the dissipative collision integral up to the second order. Beyond the second order, the results become very complicated, and a quasiparticle approach loses its attraction. We give the expressions for the effective interaction function and collision integral for statistical quasiparticles, applicable at all temperatures, and discuss the implications of this concept at high temperatures. The interaction function contains anomalous pole terms which do not exist in equations for longitudinal dynamics. This provides a somewhat unexpected interpretation for zero-temperature dissipative processes, observed recently in spin dynamics, and for controversial molecular field terms (the so-called I2 terms) as imaginary (pole) and real (principal) parts of the quasiparticle interaction function. These molecular field terms with complicated analytical structure do not vanish completely, as was assumed earlier, in the Boltzmann region, but contribute to higher-order density terms. With an emphasis on quantum gases, we discuss how to reconcile various physical assumptions inherent to different kinetic approaches to dilute gases.
Accès au bibtex
BibTex
titre
Ursell operators in statistical physics I: Generalizing the Beth Uhlenbeck formula
auteur
P. Grüter, F. Laloë
article
Journal de Physique I, 1995, 5 (2), pp.181-203. ⟨10.1051/jp1:1995120⟩
resume
The Beth Uhlenbeck formula gives an exact (quantum) expression of the second virial correction to the equation of state of a (slightly degenerate) dilute gas. We show how this result can be extended to arbitrary degeneracy provided that the interaction potential has a sufficiently short range. For this purpose we develop a formalism based on the use of Ursell operators, which contain no symmetrization in themselves (they correspond to an auxiliary system of distinguishable particles) and we show how they can be used for a system of identical particles. A concise expression generalizing the Beth Uhlenbeck formula is obtained, which is equally valid for bosons and fermions Higher order corrections are also introduced. The formalism is rather general and will be applied to other cases in forthcoming articles.
DOI
DOI : 10.1051/jp1:1995120
Accès au texte intégral et bibtex
https://hal.science/jpa-00247049/file/ajp-jp1v5p181.pdf BibTex
titre
Correlating more than two particles in quantum mechanics
auteur
Franck Laloë
article
Current Science, 1995, 68, pp.1026
resume
A few years ago, Greenberger, Horne and Zeilinger showed that quantum non locality effects, already well known for systems of two correlated particles, are more spectacular with three particles or more.\\ For observing these effects, one has to initially put the system in an entangled quantum state that is very specific, and not necessarily easy to produce.\\ We discuss some properties of these states and we propose an experimental scheme which allows to create them by succcessive applications of the postulate of measurement in quantum mechanics.\\ The procedure should in principle allow the creation of the desired correlations in systems containing a relatively large number of particles; we propose to apply it to single paramagnetic ions stored in traps, through the measurement of the rotation of the plane of polarization of a laser beam interacting with the ions (quantized Faraday effect).
Accès au texte intégral et bibtex
https://hal.science/hal-00001443/file/Ghz-fig.pdf BibTex
titre
Analysis of Certain Binary Collision Approximation Closures of the BBGKY Hierarchy
auteur
Robert F. Snider, William J. Mullin, Franck Laloë
article
Physica A: Statistical Mechanics and its Applications, 1995, 218, pp.155
resume
Boercker and Dufty (BD) introduce a binary collision approximation into the BBGKY hierarchy in order to describe the low-density behaviour of a quantum gas. Their approach involves the three-particle reduced density operator being approximated in a particular manner that favours correlation between two of the particles, while ignoring the correlation with the third. The tradition of previous derivations, on the other hand, has been to neglect the three-particle term altogether and assume a generalized form of Boltzmann's Stosszahlansatz. Both formalisms reach the same final result: the Waldmann-Snider equation (WS), a quantum version of the Boltzmann equation. We compare the two derivations in two ways: (a) by finding iterated series solutions of the BBGKY hierarchy and of the Boltzmann equation, which demonstrates what kind of terms are absent in the WS and BD approaches in comparison with exact dynamics; (b) by computing an exact correction to the WS equation, which vanishes in the BD scheme provided the mean time of duration of a collision is much shorter than the mean free time between collisions. This correction is shown to be related to the standard three-body collision integral arising in the theory of the density corrections to the Boltzmann equation. We also comment on the related work of Klimontovich, who introduces an approximation analogous to that of Boercker and Dufty.
Accès au texte intégral et bibtex
https://hal.science/hal-00001461/file/snider-mullin-laloe.pdf BibTex
titre
Ursell Operators in Statistical Physics II: Microscopic Properties of a Dilute Quantum Gas
auteur
P. Grüter, F. Laloë
article
Journal de Physique I, 1995, 5 (10), pp.1255-1279. ⟨10.1051/jp1:1995196⟩
resume
We apply the formalism of Ursell operators, introduced in a previous article, to the calculation of reduced density operators (one and two-body density operators) in a dilute quantum gas; the calculation is not a fugacity expansion and is therefore not limited to low degrees of degeneracy. We obtain quantum corrections for the one-particle density operator as a function of the second Ursell operator. For the two-body density operator, we examine how statistics and interactions combine their effects on the correlations between particles; in particular we discuss in detail how hard cores potentials affect the short range correlations, a non-perturbative effect.
DOI
DOI : 10.1051/jp1:1995196
Accès au texte intégral et bibtex
https://hal.science/jpa-00247135/file/ajp-jp1v5p1255.pdf BibTex

Conference papers

titre
Spin dynamics in spin polarized Fermi gases
auteur
A.E. Meyerovich, S. Stepaniants, Franck Laloë
article
Symposium on Quantum Fields, 1995, Ithaca, United States
Accès au bibtex
BibTex
titre
Fermi liquid effects in spin polarized gases
auteur
A.E. Meyerovich, S. Stepaniants, Franck Laloë
article
ESF conference on quantum liquids, 1995, Trieste, Italy
Accès au bibtex
BibTex
titre
Dilute degenerate gases
auteur
Franck Laloë
article
Bose-Einstein condensation, 1995, United States
Accès au bibtex
BibTex

1994

Journal articles

titre
Influence des non-linéarités sur les caractéristiques d'oscillation des instruments à vent
auteur
Noël Grand, Joël Gilbert, Franck Laloë
article
Journal de Physique Colloque, 1994, C5, pp.585
Accès au bibtex
BibTex
titre
Influence des non-linéarités sur les caractéristiques des oscillations des instruments à vent
auteur
Noël Grand, Joël Gilbert, Franck Laloë
article
Journal de Physique IV Proceedings, 1994, C5, pp.585
resume
Two simple equations give the minimal modelisation of the acoustical behaviour of woodwind instruments. We discuss the predictions of these equations on the characteristics of the small oscillations, in particular their quasisinusoidal character or finite harmonic content, and stability. We show that, instead of predicting a unique and simple standard behaviour, they introduce a whole series of possible cases, depending on the characteristics of the non linearity and of the resonator.
Accès au texte intégral et bibtex
https://hal.science/hal-00002510/file/NOEL.pdf BibTex

1991

Journal articles

titre
A kinetic equation for quantum gases (spin and statistics)
auteur
P. Nacher, G. Tastevin, F. Laloë
article
Journal de Physique I, 1991, 1 (2), pp.181-209. ⟨10.1051/jp1:1991124⟩
resume
We generalize our previous work on the compatibilty of kinetic equations with second virial corrections to the inclusion of spin and particle indistinguishability; the system is supposed to be sufficiently dilute for higher order virial density corrections (interactions and statistics) to be negligible. We show that the general idea of the “free Winger transform” can be extended to this situation; the function which appears in the kinetic equation becomes here a matrix which acts in the space of spin states of the particles. Assuming that the collisions are described by a hamiltonian which does not act on the spins (a very good approximation for nuclear spins), we write explicitly a kinetic equation which is valid for this case. The right hand side of the equation is an 18 dimension integral, as for spinless distinguishable particles, but here it contains an additional term due to statistics, which introduces commutators and anticommutators. We discuss the local conservation laws in this formalism and find, as expected, a total number of 8 conserved quantities for spin 1/2 particles (including three components of the magnetization). When the gas is at equilibrium, we obtain a pressure dependence which is in agreement with known calculations on spin polarized gases. We finally study the gradient expansion of the collision integral, and show that the zero-order (local) part is identical with the 4 terms (including identical spin rotation terms) obtained previously by Lhuillier et al. The first order (non-local) part contains many terms, wich we compare with those obtained by Silin in a context more closely related to the Landau theory.
DOI
DOI : 10.1051/jp1:1991124
Accès au texte intégral et bibtex
https://hal.science/hal-00008971/file/ajp-jp1v1p181.pdf BibTex
titre
Kinetic theory for quantum gases
auteur
Geneviève Tastevin, Pierre-Jean Nacher, Franck Laloë
article
Annalen der Physik, 1991, 48, pp.149
Accès au bibtex
BibTex
titre
A Kinetic Equation for Quantum Gases
auteur
Pierre-Jean Nacher, G. Tastevin, F. Laloë
article
Annalen der Physik, 1991, 48 (1-3), pp.149--168
resume
We apply the formalism of the free Wigner transform to the derivation of a kinetic equation valid for dilute quantum gases; this formalism is compatible with a precise treatment of two-body correlations and allows the inclusion of second virial corrections. We generalize the results obtained in previous articles where the calculation of the collision integral was limited to zero ("local") and first order gradient terms; here we use a more general ("non-local") form for the interaction term which is an integral of higher dimension (18). The conservation laws are studied in this formalism, which implies non-linear expressions for the local hydrodynamic quantities in terms of the function appearing in the kinetic equation. The pressure at thermal equilibrium is then evaluated and found to be equal to the value predicted by the Beth-Uhlenbeck formula, without adjusting any free parameter of the theory.
Accès au bibtex
BibTex

1990

Journal articles

titre
Sound velocity in spin-polarized quantum gases
auteur
Franck Laloë, Gérard Vermeulen, Matthias Elbel
article
Zeitschrift fuer Physik D, 1990, 15, pp.13
Accès au bibtex
BibTex
titre
On the Snider equation
auteur
Franck Laloë, William J. Mullin
article
Journal of Statistical Physics, 1990, 59, pp.725
Accès au bibtex
BibTex
titre
Longitudinal relaxation times for dilute quantum gases
auteur
William J. Mullin, Franck Laloë, Michael G. Richards
article
Journal of Low Temperature Physics, 1990, 80, pp.1
Accès au bibtex
BibTex
titre
Acoustical impedance measurements using the two microphone three calibration method
auteur
Vincent Gibiat, Franck Laloë
article
Journal of the Acoustical Society of America, 1990, 88, pp.2533
resume
We discuss a method for measuring the acoustical impedance of wood-wind instruments which is relatively fast and insensitive to the ambient acoustical noise.
Accès au texte intégral et bibtex
https://hal.science/hal-00008940/file/TMTC.pdf BibTex
titre
Longitudinal relaxation times for dilute quantum gases
auteur
William J. Mullin, Franck Laloë, Michael G. Richards
article
Physica B: Condensed Matter, 1990, 165, pp.725
Accès au bibtex
BibTex
titre
Mesures d'impédances, de fonctions de réflexion et d'harmonicité d'instruments à vent
auteur
V. Gibiat, Franck Laloë
article
Journal de Physique Colloque, 1990, 51 (C2), pp.C2-825-C2-828. ⟨10.1051/jphyscol:19902191⟩
resume
La méthode de mesure de l'impédance d'entrée des instruments à vent dite T.M.T.C. que nous avons développé récemment permet grâce à deux mesures simultanées de pression et à une calibration en trois points d'obtenir l'impédance d'entrée d'instruments à vent de diamètres variés avec un seul dispositif de mesure dont les imperfections géométriques acoustiques et électriques sont automatiquement prises en compte. L'utilisation systématique de la micro-informatique et de la saisie numérique permet de disposer d'un outil souple et rapide. Il est ainsi possible de calculer à partir de la mesure d'impédance la fonction de réflexion de l'instrument étudié ainsi que toute autre fonction temporelle. La mesure précise des positions des maximums d'impédance peut également être interprétée en fonction de leur rang et donner une indication sur l'harmonicité ou l'inharmonicité des résonances de l'instrument et donc sur sa qualité.
DOI
DOI : 10.1051/jphyscol:19902191
Accès au texte intégral et bibtex
https://hal.science/jpa-00230507/file/ajp-jphyscol199051C2191.pdf BibTex

1989

Journal articles

titre
Optical pumping of helium with arc lamp excited LNA lasers
auteur
Carl C. G. Aminoff, C. Larat, M. Leduc, F. Laloë
article
Revue de Physique Appliquée, 1989, 24 (8), pp.827-831. ⟨10.1051/rphysap:01989002408082700⟩
resume
We have developed a compact and relatively inexpensive laser source at λ =1.083 μm, suitable for optical pumping in helium. The laser is made of an LNA crystal transversely pumped by krypton arc lamps. A cw power of 800 mW has been achieved at 1.083 μm with a 3 GHz bandwidth. A 66 % nuclear polarization has been obtained in a 3He gas.
DOI
DOI : 10.1051/rphysap:01989002408082700
Accès au texte intégral et bibtex
https://hal.science/jpa-00246105/file/ajp-rphysap_1989_24_8_827_0.pdf BibTex
titre
Une équation cinétique pour les gaz quantiques
auteur
Geneviève Tastevin, Pierre-Jean Nacher, Franck Laloë
article
Journal de Physique, 1989, 50, pp.1879
resume
This article is the second of a series where we propose a theory of the dynamics of quantum gases with a precise treatment of the short range two body correlations. For this purpose, we use a variant of the Wigner transform, the "free transform" , which has a useful property in this context: if, before collision, two particles are uncorrelated, the incoming part of the free Wigner transform remains always exactly factorized. Therefore, instead of asssuming a factorization of the two particle distribution, it is less restrictive to make a similar assumption on the free transform. Time symmetry is broken when the correlations of the outgoing part of the free transform are ignored; this approximation, which is well in the spirit of Boltzmann, amounts to considering successive collisions as independent processes (the correlations present in the outgoing part could play a role if the same particles rapidly collided again, an unlikely event in dilute gases). Therefore, the succession of collisions is not treated exactly, but each collision is, even during interaction. One then obtains a closed set of equations which leads directly to a kinetic equation for the free distribution $ f $. The equation includes retardation and quantum refraction effects, and provides a generalization of the Boltzmann equation. The reconstruction of the two particle distribution function $ f_{II} $ from $ f $ reintroduces the effects of short range correlations and, more generally, gives the values of all one particle and two particle physical observables. The price to pay for not using the usual one particle distribution is that the relation between the local physical quantities (density of particles, energy density, etc.) becomes more complicated than in the usual theory, and includes terms which are non linear in $ f $. We nevertheless show how this formalism automatically satisfies the local conservation of all hydrodynamic quantities: particle, momentum and energy densities. The pressure tensor includes quadratic terms which correspond to second virial corrections. The temperature of the gas is defined from the kinetic energy of the particles when they are far apart from each other. We finally briefly discuss the connections of this formalism with the classical Enskog theory, or mean field type theories such as the Landau theory (in particular, we note the presence of recoil effects in the "molecular field")
Accès au texte intégral et bibtex
https://hal.science/hal-00001438/file/WIGNER-2.pdf BibTex
titre
La transformée de Wigner libre, évolution dans une collision
auteur
F. Laloë
article
Journal de Physique, 1989, 50 (14), pp.1851-1878. ⟨10.1051/jphys:0198900500140185100⟩
resume
Le but général de la série d'articles dont celui-ci est le premier est de décrire la dynamique hors d'équilibre des gaz quantiques dilués en tenant compte de façon précise des corrélations binaires entre particules ; ces corrélations sont généralement ignorées dans les approches théoriques du type Boltzmann. Nous proposons pour cela l'utilisation d'une variante de la transformée de Wigner, la transformée de Wigner libre, qui « efface » les corrélations à courte distance créées par le potentiel d'interaction entre particules. Ainsi, chaque fois qu'avant collision la transformée libre était factorisée, une factorisation subsiste rigoureusement pendant toute la collision ; elle se prête donc mieux que la transformée habituelle à une hypothèse de « chaos moléculaire » à la Boltzmann. Une fois connue la transformée libre, les corrélations entre particules peuvent être reconstruites et leurs effets physiques calculés. L'étude de l'évolution de la transformée de Wigner libre dans une collision binaire conduit à des résultats qui s'expriment complètement en fonction des caractéristiques de la matrice T « sur la couche de masse » (matrice S, déphasages), même lorsque les particules sont en train d'interagir. En sus des termes habituels de collision où apparaissent comme dans l'équation de Boltzmann les sections efficaces de collision, le calcul donne des termes dus aux effets de retard, et aux effets « de réfraction » dans la collision. Ces termes joueront un rôle essentiel dans l'équation cinétique proposée dans l'article suivant, et dans les corrections du viriel aux propriétés d'équilibre et de transport du gaz.
DOI
DOI : 10.1051/jphys:0198900500140185100
Accès au texte intégral et bibtex
https://hal.science/jpa-00211035/file/ajp-jphys_1989_50_14_1851_0.pdf BibTex
titre
Dynamique des gaz quantiques (particules discernables sans spin)
auteur
Pierre-Jean Nacher, Geneviève Tastevin, Franck Laloë
article
Journal de Physique, 1989, 50, pp.1907
resume
Nous appliquons les résultats de deux articles précédents, en particulier uneéquation cinétique généralisant l'équation de Boltzmann, à l'étude des gaz dilués quantiques hors d'équilibre. Par une simple extension de la méthode de Chapman Enskog appliquée à cette équation cinétique, nous calculons les propriétés hydrodynamiques du gaz. A l'ordre le plus bas (hydrodynamique d'Euler), nous obtenons des résultats pour la pression, la vitesse du son et la capacité calorifique qui, contrairement à ceux de la théorie de Boltzmann, contiennent les secondes corrections du viriel. A l'ordre suivant (hydrodynamique visqueuse, ou de Navier Stokes), nous obtenons les corrections du premier ordre en densité aux coefficients de transport, et montrons qu'il peut exister un terme de seconde viscosité, quadratique en densité. Ce formalisme donne accès aux parties des corrections du viriel des coefficients de transport qui dépendent des collisions à deux corps, mais pas à celles qui sont dues aux collisions ternaires. Il est quantique et permet de réobtenir l'expression de Beth et Uhlenbeck de la seconde correction du viriel en fonction des déphasages.
Accès au texte intégral et bibtex
https://hal.science/hal-00001436/file/WIGNER-3.pdf BibTex
titre
Dynamics of Quantum Gases (Distinguishable Particles without Spin)
auteur
Pierre-Jean Nacher, G. Tastevin, F. Laloe
article
Journal de Physique, 1989, 50 (14), pp.1907--1941
Accès au bibtex
BibTex
titre
Dynamique des gaz quantiques (particules discernables sans spin)
auteur
P.J. Nacher, G. Tastevin, F. Laloë
article
Journal de Physique, 1989, 50 (14), pp.1907-1941. ⟨10.1051/jphys:0198900500140190700⟩
resume
Nous appliquons les résultats de deux articles précédents, en particulier une équation cinétique généralisant l'équation de Boltzmann, à l'étude des gaz dilués quantiques hors d'équilibre. Par une simple extension de la méthode de Chapman Enskog appliquée à cette équation cinétique, nous calculons les propriétés hydrodynamiques du gaz. A l'ordre le plus bas (hydrodynamique d'Euler), nous obtenons des résultats pour la pression, la vitesse du son et la capacité calorifique qui, contrairement à ceux de la théorie de Boltzmann, contiennent les secondes corrections du viriel. A l'ordre suivant (hydrodynamique visqueuse, ou de Navier Stokes), nous obtenons les corrections du premier ordre en densité aux coefficients de transport, et montrons qu'il peut exister un terme de seconde viscosité, quadratique en densité. Ce formalisme donne accès aux parties des corrections du viriel des coefficients de transport qui dépendent des collisions à deux corps, mais pas à celles qui sont dues aux collisions ternaires. Il est quantique et permet de réobtenir l'expression de Beth et Uhlenbeck de la seconde correction du viriel en fonction des déphasages.
DOI
DOI : 10.1051/jphys:0198900500140190700
Accès au texte intégral et bibtex
https://hal.science/jpa-00211037/file/ajp-jphys_1989_50_14_1907_0.pdf BibTex

Conference papers

titre
Kinetic theory of quantum gases: beyond the Boltzmann equation
auteur
Geneviève Tastevin, Pierre-Jean Nacher, Franck Laloë
article
SPOQS III, 1989, Torino, Italy. pp.310
Accès au bibtex
BibTex

1988

Journal articles

titre
Obtaining polarized liquid helium 3 from optically oriented gas
auteur
G. Tastevin, P.J. Nacher, L. Wiesenfeld, M. Leduc, F. Laloë
article
Journal de Physique, 1988, 49 (1), pp.1-6. ⟨10.1051/jphys:019880049010100⟩
resume
Spin polarized liquid helium three can be obtained by liquefaction of a gas polarized by laser optical pumping. We show that this method can lead to nuclear polarizations exceeding 40 % in a liquid at about 400 mK and almost zero pressure. The relaxation time of the orientation is a few minutes, comparable to the relaxation time of weakly polarized bulk liquid. The NMR signals given by the liquid are strongly shifted in frequency ; this provides a precise and convenient way to measure the polarization and to follow the motion of the liquid inside the experimental cell.
DOI
DOI : 10.1051/jphys:019880049010100
Accès au texte intégral et bibtex
https://hal.science/jpa-00210670/file/ajp-jphys_1988_49_1_1_0.pdf BibTex
titre
Obtaining polarized liquid 3He from optically oriented gas
auteur
Geneviève Tastevin, Pierre-Jean Nacher, Laurent Wiesenfeld, Michèle Leduc, Franck Laloë
article
Journal de Physique, 1988, 49, pp.1
Accès au bibtex
BibTex

1987

Journal articles

titre
Heat Conduction Changes in Spin-Polarized Gaseous He-3
auteur
M. Leduc, Pierre-Jean Nacher, D. S. Betts, J.M. Daniels, F. Laloe
article
Japanese Journal of Applied Physics, 1987, 26, pp.213--214
Accès au bibtex
BibTex
titre
Spin-polarized 3He : liquid gas equilibrium
auteur
S. Stringari, M. Barranco, A. Polls, P.J. Nacher, F. Laloë
article
Journal de Physique, 1987, 48 (8), pp.1337-1350. ⟨10.1051/jphys:019870048080133700⟩
resume
We study the effects of nuclear polarization M on the liquid-gas equilibrium phase diagram of 3He, in situations where the saturating vapour pressure increases or decreases as a function of M, and where a metamagnetic instability may occur in the liquid phase. Numerical predictions are given within the frame of a phenomenological model with parameters fitted to reproduce accurately the saturating vapour pressure of the unpolarized liquid as well as its magnetic susceptibility. At temperatures of the order of 0.5 K situations are found where interesting phenomena such as liquid overpolarization and metamagnetic plateaus occur.
DOI
DOI : 10.1051/jphys:019870048080133700
Accès au texte intégral et bibtex
https://hal.science/jpa-00210560/file/ajp-jphys_1987_48_8_1337_0.pdf BibTex
titre
Phase Transitions In Partially Spin-Polarized 3he
auteur
M. Barranco, A. Polls, S. Stringari, P. Nacher, F. Laloë
article
Journal de Physique Colloque, 1987, 48 (C2), pp.C2-101-C2-106. ⟨10.1051/jphyscol:1987216⟩
resume
We present liquid-gas equilibrium phase diagrams for partially spin-polarized 3He. At low temperatures, interesting phenomena such as liquid metamagnetism and liquid overpolarization have been found.
DOI
DOI : 10.1051/jphyscol:1987216
Accès au texte intégral et bibtex
https://hal.science/jpa-00226481/file/ajp-jphyscol198748C216.pdf BibTex
titre
Nuclear Polarization and Heat Conduction Changes in Gaseous He-3
auteur
M. Leduc, Pierre-Jean Nacher, D. S. Betts, J.M. Daniels, F. Laloe
article
EPL - Europhysics Letters, 1987, 4 (1), pp.59--64
Accès au bibtex
BibTex
titre
Spin polarized 3He: liquid gas equilibrium
auteur
Sandro Stringari, Manuel Barranco, A. Polls, Pierre-Jean Nacher, Franck Laloë
article
Journal de Physique Colloque, 1987, C2, pp.101
Accès au bibtex
BibTex
titre
Spin polarized 3He: liquid gas equilibrium
auteur
Sandro Stringari, Manuel Barranco, A. Polls, Pierre-Jean Nacher, Franck Laloë
article
Journal de Physique, 1987, 48, pp.1337
Accès au bibtex
BibTex
titre
Nuclear polarization and heat conduction changes in gaseous 3He
auteur
Michèle Leduc, Pierre-Jean Nacher, David Betts, James M. Daniels, Geneviève Tastevin, Franck Laloë
article
EPL - Europhysics Letters, 1987, 4, pp.59
Accès au bibtex
BibTex

Conference papers

titre
La polarisation des spins nucléaires: une cause microscopique d'effets macroscopiques
auteur
Franck Laloë
article
Interaction of Radiation with Matter, 1987, Pise, Italie
Accès au bibtex
BibTex

1986

Journal articles

titre
Localisation d'Anderson des ondes dans les réseaux acoustiques unidimensionnels aléatoires
auteur
C. Depollier, Jean Kergomard, Franck Laloë
article
Annales de Physique, 1986, 11, pp.457. ⟨10.1051/anphys:01986001105045700⟩
DOI
DOI : 10.1051/anphys:01986001105045700
Accès au bibtex
BibTex
titre
Bifurcations, Period doubling and chaos in clarinet-like systems
auteur
Christian Maganza, René Caussé, Franck Laloë
article
EPL - Europhysics Letters, 1986, 1, pp.295-302
resume
Wind instruments provide interesting hydrodynamical systems where non-linearities are important but well localized. A simple analysis shows that these systems should undergo Feignebaum-type route to chaos, with a cascade of period doublings. Experiments have been performed fo confirm these predictions
Accès au texte intégral et bibtex
https://hal.science/hal-00221496/file/maganza-manuscrit.pdf BibTex
titre
Quantum Properties of Spin-Polarized He-3 Optically Oriented by a LNA Laser
auteur
M. Leduc, F. Laloe, Pierre-Jean Nacher, G. Tastevin, J. M. Daniels, D. Betts
article
Journal of the Optical Society of America B, 1986, 3 (8), pp.P138--P140
Accès au bibtex
BibTex

Conference papers

titre
Infrared tunable lasers for helium three optical pumping
auteur
Franck Laloë, Michèle Leduc, James M. Daniels, Pierre-Jean Nacher
article
Montana workshop on Polarized targets and beam sources, 1986, United States
Accès au bibtex
BibTex
titre
A new infrared tunable laser (LNA) for optical pumping in Helium
auteur
Franck Laloë, Michèle Leduc, James M. Daniels
article
CLEO 86, 1986, San Francisco, United States
Accès au bibtex
BibTex

Books

titre
Mécanique quantique
auteur
Claude Cohen-Tannoudji, Bernard Diu, Franck Laloë
article
Centre de Publications Universitaire, Téhéran, pp.600 environ, 1986
Accès au bibtex
BibTex

1985

Journal articles

titre
Direct detection of spin waves in gaseous 3He↑
auteur
G. Tastevin, P.J. Nacher, M. Leduc, F. Laloë
article
Journal de Physique Lettres, 1985, 46 (6), pp.249-254. ⟨10.1051/jphyslet:01985004606024900⟩
resume
In gaseous spin-polarized 3He at low temperature, spin-diffusion becomes oscillatory and gives rise to spin waves; these waves have a quality factor μM, where M is the (relative) nuclear magnetization and μ a dimensionless coefficient characteristic of the importance of exchange effects in binary collisions. We describe here an NMR technique where these oscillatory modes are directly excited and detected, with the use of two sets of radiofrequency coils (for induction and detection), each connected in opposition in order to create or detect pure magnetization gradients over the sample. The measurements of μ are in good agreement with theory as well as with previous experiments, but only at temperatures above 2 K; below, the measurements are affected by processes which are not fully understood, probably related to the formation of a 3He monolayer on the surface of the coating of solid hydrogen which covers the inner surface of the cell.
DOI
DOI : 10.1051/jphyslet:01985004606024900
Accès au texte intégral et bibtex
https://hal.science/jpa-00232507/file/ajp-jphyslet_1985_46_6_249_0.pdf BibTex
titre
Spin oscillations in polarized gases
auteur
Claire C. Lhuillier, Franck Laloë
article
Physical Review Letters, 1985, 54, pp.1207
Accès au bibtex
BibTex
titre
Relaxation nucléaire de 3He gazeux sur H2 solide
auteur
V. Lefèvre-Seguin, P.J. Nacher, J. Brossel, W.N. Hardy, F. Laloë
article
Journal de Physique, 1985, 46 (7), pp.1145-1172. ⟨10.1051/jphys:019850046070114500⟩
resume
Cet article présente une étude expérimentale détaillée de la relaxation-paroi sur des surfaces de H2 solide d'un gaz dilué de 3He, orienté par pompage optique. La grandeur mesurée dans ces expériences est le temps de relaxation global T1 de l'orientation nucléaire de l'échantillon de 3He, lié directement au temps de relaxation Ta de la phase adsorbée (composée d'atomes de 3He adsorbés à la surface de H2 solide). L'étude des variations de T1 en fonction de la température permet de déterminer expérimentalement l'énergie d'adsorption d'un atome de 3He sur H2 solide : ΔW (3He/H2) = 12 ± 3 K. Des expériences complémentaires sur D2 et Ne solides sont également présentées qui conduisent à une mesure de ΔW (3He/D2) = 20 ± 3 K et ΔW (3He/Ne) = 38 ± 5 K, l'ensemble de ces valeurs expérimentales concordant bien avec les prédictions théoriques existantes.
DOI
DOI : 10.1051/jphys:019850046070114500
Accès au texte intégral et bibtex
https://hal.science/jpa-00210057/file/ajp-jphys_1985_46_7_1145_0.pdf BibTex
titre
Optical pumping of 3He nuclei
auteur
Franck Laloë, Michèle Leduc, Pierre-Jean Nacher, Leonid Novikov
article
Uspehi Fiziceskih Nauk, 1985, 147, pp.433
Accès au bibtex
BibTex

1984

Journal articles

titre
Propagation des ondes dans les tuyaux sonores percés de trous latéraux irréguliers
auteur
C. Depollier, Jean Kergomard, J.C. Lesueur, Franck Laloë
article
Revue du Cethedec, 1984, 79, pp.67
Accès au bibtex
BibTex
titre
Quel usage les physiciens font-ils de la mécanique quantique ?
auteur
Franck Laloë
article
Fundamenta Scientiae, 1984, 5, pp.17
Accès au bibtex
BibTex
titre
Nuclear Polarization in Gaseous 3He by Optical Pumping
auteur
Michèle Leduc, Stuart B Crampton, Pierre-Jean Nacher, Franck Laloë
article
Nuclear Science Applications A, 1984, 2, pp.1--20
resume
Optical pumping can provide significant nuclear polarizations in gaseous 3He. This method, developed by Colegrove, Schearer and Walters 20 years ago, can be applied to the realization of polarized targets for nuclear physics or neutron spin state filters. Moreover, highly polarized discharges in gaseous helium can be used as sources of polarized beams of atomic or molecular ions or electrons. Some progress has been made recently to obtain higher nuclear polarizations in gaseous 3He at a higher density. Laser optical pumping can produce polarizations over 60% or more in a gas at room temperature. This can be combined with a polarization transfer technique, in which a laser is used to pump 3He in a cell at room temperature, while another cell at a few degrees Kelvin is polarized by diffusion of the atoms through a long connecting tube. Cryogenic coatings, made of solid hydrogen frozen on the coldest parts of the inside wall of the container, reduce very effectively the fast nuclear relaxation which would occur on bare pyrex walls at low temperatures. Nuclear polarizations of the order of 50% have been obtained in a relatively dense gas (n ~ 10^18 cm-3) at T <= 4 K. Higher densities should be attainable by optical pumping at higher gas pressures and, possibly, by subsequent compression of the gas at low temperature.
Accès au texte intégral et bibtex
https://hal.science/hal-01383488/file/Crampton_NuclSciAppl84_compact.pdf BibTex
titre
Spin rotation effects and spin waves in gaseous 3He↑
auteur
P.J. Nacher, G. Tastevin, M. Leduc, S.B. Crampton, F. Laloë
article
Journal de Physique Lettres, 1984, 45 (9), pp.441-448. ⟨10.1051/jphyslet:01984004509044100⟩
resume
Spin polarized gases such as H↑ or 3He↑ can propagate damped spin waves at low temperatures; their origin is the so-called « identical spin rotation effect » in collisions between identical particles. We report here the observation of such effects in 3He↑ in the temperature range 2 < T < 6 K, and preliminary measurements of the coefficient μ which characterizes the quality factor of the spin oscillations. The measurements are in agreement with the numerical calculations of C. Lhuillier.
DOI
DOI : 10.1051/jphyslet:01984004509044100
Accès au texte intégral et bibtex
https://hal.science/jpa-00232367/file/ajp-jphyslet_1984_45_9_441_0.pdf BibTex

Conference papers

titre
Laser optical pumping of 3He
auteur
Franck Laloë, Pierre-Jean Nacher, Michèle Leduc, Laird D. Schearer
article
Workshop on polarized 3He beams and targets for nuclear physics, 1984, Princeton, United States
Accès au bibtex
BibTex
titre
Nuclear polarization of 3He gas at and below 4.2K by room temperature laser optical pumping
auteur
Michèle Leduc, Stuart B. Crampton, Pierre-Jean Nacher, Franck Laloë
article
SANIBEL Conference and TRIUMF meeting, 1984, Vancouver, Canada
Accès au bibtex
BibTex
titre
Observation of spin waves in gaseous 3He
auteur
Pierre-Jean Nacher, Geneviève Tastevin, Michèle Leduc, Stuart B. Crampton, Franck Laloë
article
LT 17, 1984, Karlsruhe, Germany
Accès au bibtex
BibTex

1983

Journal articles

titre
Détection de la rotation Faraday produite par un gaz placé dans un interféromètre de Michelson
auteur
M. Pinard, L. Julién, F. Laloë
article
Journal de Physique, 1983, 44 (5), pp.589-595. ⟨10.1051/jphys:01983004405058900⟩
resume
On présente une méthode permettant d'augmenter la rotation du plan de polarisation d'un faisceau lumineux produite par la traversée d'un gaz atomique doué d'un pouvoir rotatoire (par exemple un gaz orienté par pompage optique). La cellule contenant les atomes est placée dans l'un des bras d'un interféromètre de Michelson, dont la différence de marche est réglée pour que la presque totalité de la puissance lumineuse soit réfléchie vers l'arrière; si l'on détecte le faisceau lumineux, de faible intensité, défléchi à angle droit par l'interféromètre, on observe alors une rotation accrue du plan de polarisation. Après une discussion générale de l'effet, on décrit des expériences de pompage optique d'atomes de néon métastables où il a été mis en évidence. Des augmentations de la rotation du plan de polarisation atteignant un facteur 30 ont été observées.
DOI
DOI : 10.1051/jphys:01983004405058900
Accès au texte intégral et bibtex
https://hal.science/jpa-00209635/file/ajp-jphys_1983_44_5_589_0.pdf BibTex
titre
Nuclear polarization through optical pumping of gaseous 3He below 1 K
auteur
M. E. Himbert, V. Lefevre-Seguin, P.J. Nacher, J. Dupont-Roc, M. Leduc, F. Laloë
article
Journal de Physique Lettres, 1983, 44 (13), pp.523-529. ⟨10.1051/jphyslet:019830044013052300⟩
resume
We have extended to temperatures below 1 K the optical pumping technique for polarizing the nuclei pf ground state 3He atoms in the gas phase. A superfluid 4He film covering the surface of the pyrex cell protected the 3He atoms from the rapid depolarization processes that would be experienced in the presence of bare pyrex walls. Relatively long relaxation times of order 103 s were observed at temperatures down to 500 mK, the lowest temperature accessible with the present apparatus.
DOI
DOI : 10.1051/jphyslet:019830044013052300
Accès au texte intégral et bibtex
https://hal.science/jpa-00232226/file/ajp-jphyslet_1983_44_13_523_0.pdf BibTex

1982

Journal articles

titre
Transport properties in a spin polarized gas (I)
auteur
Claire C. Lhuillier, Franck Laloë
article
Journal de Physique, 1982, 43, pp.197-224
resume
On étudie l'influence des effets d'indiscernabilité des atomes sur les propriétés de transport dans un gaz orienté à basse termpérature, l'hélium trois pas exemple, le gaz étant supposé dilué et donc non-dégénéré. Dans ce but, on commence par étudier en détail les effets d'une collision binaire...
Accès au texte intégral et bibtex
https://hal.science/hal-00003386/file/LL-I-82.pdf BibTex
titre
Le second coefficient du viriel de H atomique ; effet des variables internes
auteur
V. Lefèvre-Seguin, P.J. Nacher, C. Lhuillier, F. Laloë
article
Journal de Physique, 1982, 43 (8), pp.1199-1211. ⟨10.1051/jphys:019820043080119900⟩
resume
On considère un gaz d'atomes d'hydrogène supposé stable (pas de recombinaison moléculaire), dont les variables internes de spins électronique et nucléaire sont décrites par un opérateur densité fixé ρSI. Les atomes étant chacun constitué d'une paire de fermions (un proton et un électron), non indissociable du fait de l'existence des collisions d'échange de spin, leur comportement de bosons n'est pas évident. Le but de cet article est de discuter dans quelle mesure la pression du gaz est effectivement celle d'un gaz de bosons indissociables, dans le cadre d'un calcul limité à celui du second coefficient du viriel (correction du second ordre en densité pour un gaz dilué). On trouve que ce coefficient comprend en fait plusieurs termes, soit de statistique pure (effets d'indiscernabilité en l'absence d'interaction entre atomes), soit d'interaction et de statistique combinées (effets des potentiels Vg et Vu). Tous ces termes dépendent explicitement des valeurs moyennes d'un certain nombre d'opérateurs de spin, calculables à partir de ρSI. Le terme de statistique pure, dominant à très basse température, correspond à l'échange d'atomes complets (échange simultané de leurs protons et de leurs électrons), ce qui explique son caractère bosonique. En revanche, dans les termes liés aux interactions apparaissent, non seulement des contributions provenant de l'échange d'atomes complets, mais également des contributions liées à l'échange d'un type de particule seulement (protons ou électrons) qu'on peut relier aux effets des collisions d'échange de spin.
DOI
DOI : 10.1051/jphys:019820043080119900
Accès au texte intégral et bibtex
https://hal.science/jpa-00209497/file/ajp-jphys_1982_43_8_1199_0.pdf BibTex
titre
Relaxation nucléaire de 3He ↑ dans un champ magnétique inhomogène
auteur
V. Lefevre-Seguin, P.J. Nacher, F. Laloë
article
Journal de Physique, 1982, 43 (5), pp.737-753. ⟨10.1051/jphys:01982004305073700⟩
resume
On présente dans cet article une étude théorique de la relaxation de spin d'un gaz atomique dilué, produite par un gradient de champ magnétique de faible intensité. La théorie est valide à la fois en champ faible ou modéré (cas où le temps de corrélation du gaz qui joue un rôle est le temps de diffusion dans son récipient) et en champ fort (c'est alors le temps entre collisions qui joue le rôle essentiel). Elle tient compte des effets quantiques d'indiscernabilité des atomes. Si les effets de divergence du libre parcours moyen dans un gaz polarisé à température nulle ne jouent ici aucun rôle, contrairement à ce qui se produit pour la viscosité par exemple, les effets de « rotation des spins identiques » peuvent être importants.
DOI
DOI : 10.1051/jphys:01982004305073700
Accès au texte intégral et bibtex
https://hal.science/jpa-00209446/file/ajp-jphys_1982_43_5_737_0.pdf BibTex
titre
Transport properties in a spin polarized gas (II)
auteur
Claire C. Lhuillier, Franck Laloë
article
Journal de Physique, 1982, 43, pp.225-241
resume
The general results obtained in a preceding article (with the same title) are appliede to the study of transport phenomena in a spin polarized gas at low temperature, with particular emphasis on particle indistinguishability effects in collisions. A simple theory of spin diffusion is pressented and the response of the gas to a spin orientation gradient is calculated, taking into account the "identical spin rotation effect". The hydrodynamic equations of evolution of the spin orientation give rise to oscillations (spin waves). .....
Accès au texte intégral et bibtex
https://hal.science/hal-00003387/file/LL-II-82.pdf BibTex
titre
Pompage optique doublement sélectif en vitesses
auteur
M. Pinard, L. Julien, F. Laloë
article
Journal de Physique, 1982, 43 (4), pp.601-629. ⟨10.1051/jphys:01982004304060100⟩
resume
La méthode du pompage optique sélectif en vitesses est étendue à la sélection de deux composantes de la vitesse des atomes, grâce à l'utilisation de deux faisceaux de pompage de directions différentes, et à l'observation d'effets croisés non linéaires, proportionnels à l'intensité de chacun des faisceaux. Un troisième faisceau, coplanaire avec les deux précédents, sert à la détection, les trois faisceaux étant issus du même laser. On obtient par cette méthode toute une série de signaux correspondant aux différentes observables atomiques (population, orientation, alignement) que l'on peut créer ou détecter, suivant le choix de la polarisation de chacun des faisceaux. On discute dans cet article la nature et la forme de ces signaux, ainsi que les conditions géométriques dans lesquelles ils ne sont pas élargis par l'effet Doppler. On décrit enfin une expérience réalisée avec des atomes de néon métastables où un certain nombre de ces signaux ont été observés.
DOI
DOI : 10.1051/jphys:01982004304060100
Accès au texte intégral et bibtex
https://hal.science/jpa-00209431/file/ajp-jphys_1982_43_4_601_0.pdf BibTex
titre
Polarisation nucléaire de 3He gazeux par pompage optique laser
auteur
P.J. Nacher, M. Leduc, Gérard Trénec, F. Laloë
article
Journal de Physique Lettres, 1982, 43 (15), pp.525-529. ⟨10.1051/jphyslet:019820043015052500⟩
resume
Une polarisation nucléaire élevée, de l'ordre de 70 %, a été obtenue par pompage optique dans 3He gazeux grâce à l'utilisation d'un laser à centres colorés (F+2* dans NaF) fournissant plusieurs centaines de milliwatts à la longueur d'onde λ = 1,08 μm.
DOI
DOI : 10.1051/jphyslet:019820043015052500
Accès au texte intégral et bibtex
https://hal.science/jpa-00232087/file/ajp-jphyslet_1982_43_15_525_0.pdf BibTex
titre
Addendum - Transport properties in a spin polarized gas, I and II
auteur
C. Lhuillier, F. Laloë
article
Journal de Physique, 1982, 43 (5), pp.833-833. ⟨10.1051/jphys:01982004305083300⟩
resume
No abstract available
DOI
DOI : 10.1051/jphys:01982004305083300
Accès au texte intégral et bibtex
https://hal.science/jpa-00209458/file/ajp-jphys_1982_43_5_833_0.pdf BibTex

1981

Journal articles

titre
Double velocity selection with optical pumping
auteur
Lucile Julien, Michel Pinard, Franck Laloë
article
Physical Review Letters, 1981, 47, pp.564
Accès au bibtex
BibTex
titre
Cadre général de la mécanique quantique, les objections de Einstein, Podolsky et Rosen
auteur
F. Laloë
article
Journal de Physique Colloque, 1981, 42 (C2), pp.C2-1-C2-40. ⟨10.1051/jphyscol:1981201⟩
resume
Ce texte est celui d'une conférence d'introduction pour non-spécialistes au cadre général de la mécanique quantique, ainsi qu'aux objections à cette théorie formulées par Einstein, Podolsky et Rosen. Après un rappel général, mais rapide, du formalisme de la mécanique quantique et de son interprétation dite de Copenhague, quelques exemples sont présentés ; on discute ensuite en détail le schéma expérimental imaginé par Einstein, Podolsky et Rosen, appliqué au cas de deux particules de spin 1/2 corrélées, ainsi que ses implications concernant les éléments de réalité physique qui peuvent être attachés au système. Pour insister sur quelques aspects inattendus du langage qu'emploie la mécanique quantique pour décrire certains types de corrélations, on présente une image macroscopique familière qui montre que les corrélations rencontrées dans la vie courante sont de nature différente (cause commune dans le passé). On discute enfin les notions de séparabilité, localité et déterminisme.
DOI
DOI : 10.1051/jphyscol:1981201
Accès au texte intégral et bibtex
https://hal.science/jpa-00220687/file/ajp-jphyscol198142C201.pdf BibTex
titre
Cadre général de la mécanique quantique ; les objections de Einstein, Podolsky et Rosen
auteur
Franck Laloë
article
Journal de Physique Colloque, 1981, 42, C2, pp.1
Accès au bibtex
BibTex

1980

Journal articles

titre
Quantum properties of spin-polarized 3He
auteur
Claire C. Lhuillier, Franck Laloë
article
Journal de Physique Colloque, 1980, 41, C7, pp.51
Accès au bibtex
BibTex
titre
Hyperfine structure and isotope shift of the 640.2 and 626.6 nm lines of neon
auteur
L. Julien, M. Pinard, F. Laloë
article
Journal de Physique Lettres, 1980, 41 (20), pp.479-482. ⟨10.1051/jphyslet:019800041020047900⟩
resume
A tunable single mode laser has been used to excite the λ = 640.2 and 626.6 nm lines of 20Ne, 21Ne and 22Ne. Using the velocity selective optical pumping method, we have measured the hyperfine structures and isotopic shifts of these two lines. We obtain the following values for the 21Ne hyperfine structure constants of the 2p 9 level : We have also measured isotope shifts and obtained values in good agreement with the mass-shift formula.
DOI
DOI : 10.1051/jphyslet:019800041020047900
Accès au texte intégral et bibtex
https://hal.science/jpa-00231826/file/ajp-jphyslet_1980_41_20_479_0.pdf BibTex
titre
The role of the Pauli principle in spin exchange collisions
auteur
M. Pinard, F. Laloë
article
Journal de Physique, 1980, 41 (8), pp.769-797. ⟨10.1051/jphys:01980004108076900⟩
resume
The effect of spin exchange collisions on the internal variables (orientation, alignment, etc.) of colliding atoms is discussed, with particular emphasis on the role played by the Pauli principle. The calculation presented is valid for distinguishable or identical particles, and the initial introduction of an effective exchange hamiltonian for the spins is avoided. The one-atom density matrix of the internal variables is calculated after collision, in an operatorial form which enables the discussion of various physical effects. The first term in the density matrix evolution is a transfer term which does not originate from particle indistinguishability. The following terms are indeed introduced by the Pauli antisymmetrization principle applied to electrons and nuclei, and they can be described as electronic or nuclear apparent magnetic field (or electric gradient). In addition, terms arising from the combined exchange of electrons and nuclei are obtained, in particular from the exchange of identical whole atoms (bosons in the case of hydrogen). The evolution equations for the density operators are applied to a few particular cases in order to evaluate spin exchange effects in various situations : weak or strong hyperfine decoupling, Zeeman or hyperfine resonances, etc...
DOI
DOI : 10.1051/jphys:01980004108076900
Accès au texte intégral et bibtex
https://hal.science/jpa-00209302/file/ajp-jphys_1980_41_8_769_0.pdf BibTex
titre
Nuclear Polarization Of A 3he Gas By Laser Optical Pumping
auteur
M. Leduc, Gérard Trénec, F. Laloë
article
Journal de Physique Colloque, 1980, 41 (C7), pp.C7-75-C7-78. ⟨10.1051/jphyscol:1980712⟩
resume
A brief introduction to the optical pumping technique as a method for nuclearly polarizing a 3He gas is given. Large polarizations should be obtainable by replacing the discharge lamps by tunable lasers as pumping sources. The characteristics of a suitable laser source are briefly discussed. Results are given for two experimental attempts : picosecond synchronous pumping of I R dye lasers and tandem pumping of newly discovered F+2 like colored center lasers.
DOI
DOI : 10.1051/jphyscol:1980712
Accès au texte intégral et bibtex
https://hal.science/jpa-00220149/file/ajp-jphyscol198041C712.pdf BibTex
titre
Quantum Properties Of Spin Polarized 3he (3he↑)
auteur
C. Lhuillier, F. Laloë
article
Journal de Physique Colloque, 1980, 41 (C7), pp.C7-51-C7-59. ⟨10.1051/jphyscol:1980710⟩
resume
The effect of a high polarization of the nuclear spins in an ensemble of 3He atoms are theoretically investigated. One can see from the Pauli antisymmetrization principle that a non-zero nuclear polarization results in an increase of the kinetic energy of the atoms and in a decrease of the effectiveness of their interactions. As a consequence, the macroscopic properties of gaseous, liquid or solid 3He at low temperatures may be significantly altered. Several examples of these changes are briefly discussed in this article : modifications of the transport properties of gaseous 3He at a few degree Kelvin, of the liquid-vapour and liquid-solid phase diagram, etc.
DOI
DOI : 10.1051/jphyscol:1980710
Accès au texte intégral et bibtex
https://hal.science/jpa-00220147/file/ajp-jphyscol198041C710.pdf BibTex
titre
The role of the Pauli principle in metastability exchange collisions
auteur
M. Pinard, F. Laloë
article
Journal de Physique, 1980, 41 (8), pp.799-818. ⟨10.1051/jphys:01980004108079900⟩
resume
In optical pumping experiments, metastability exchange collisions are used to transfer orientation, alignment, ... between different atomic levels. This article studies the effect of such collisions on the atom internal variables density operator by a method used in a previous publication for spin exchange collisions. The calculations are valid when the nuclei of the two atoms are distinguishable as well as when they are identical particles, which allows a detailed discussion of nuclear identity effects (apparent magnetic field, etc...). Two cases are successively studied : no depolarization of the electronic angular momentum (He*-He collisions) and partial depolarization (Ne*-Ne collisions for example). The nuclear identity effects should be observable in low temperature optical pumping experiments with noble gases. In an Appendix, another particle identity effect is studied, which can be observed in atomic beam experiments : during the collision of two 3He atoms, both in the ground state, the spin state of the atoms scattered in a particular direction can be changed by nuclear indistinguishability effects.
DOI
DOI : 10.1051/jphys:01980004108079900
Accès au texte intégral et bibtex
https://hal.science/jpa-00209303/file/ajp-jphys_1980_41_8_799_0.pdf BibTex

1979

Journal articles

titre
Efficient cw single mode dye laser with double or triple Michelson interferometer
auteur
Michel Pinard, Michèle Leduc, Gérard Trénec, Carl C. G. Aminoff, Franck Laloë
article
Applied Physics, 1979, 19, pp.399
Accès au bibtex
BibTex
titre
Velocity selective optical pumping and Doppler-free spectroscopy
auteur
Michel Pinard, Carl C. G. Aminoff, Franck Laloë
article
Physical Review A : Atomic, molecular, and optical physics [1990-2015], 1979, 19, pp.2366
Accès au bibtex
BibTex
titre
L'hélium trois polarisé: un "nouveau" fluide quantique?
auteur
Claire C. Lhuillier, Franck Laloë
article
Journal de Physique, 1979, 40, pp.239
resume
We study the physical properties of a 3He fluid, in which all nuclear spins are parallel to each other (fully polarized 3He). At low temperatures, significant differences can exist between of this polarized fluid and ordinary Helium 3. The origin of the differences is purely quantum mechanical and arises from the Pauli exclusion principla. At low densities, only the transport properties of eht gas are modified. At higher densities, the equilibriium propertiees (virial coefficients) are also changed by the nuclear polarisation. We also predict changes oif the liquid-vapour or liquid-solid equilibrium pressures, as well as modifications of the 3He-4He misture phase diagram. This article gives a preliminary theoretical discusion of these new effects; experimental prospects are also briefly discussed.
Accès au texte intégral et bibtex
https://hal.science/hal-00003340/file/lhuillier-laloe.pdf BibTex
titre
Optical pumping of metastable 5S Oxygen
auteur
Lucile Julien, Jean-Pierre Descoubes, Franck Laloë
article
Journal of Physics B: Atomic, Molecular and Optical Physics, 1979, 12, pp.L769
Accès au bibtex
BibTex

1978

Journal articles

titre
Double Michelson mode selector and pressure scanning of a cw single mode dye laser
auteur
Michel Pinard, Carl C. G. Aminoff, Franck Laloë
article
Applied Physics, 1978, 15, pp.371
Accès au bibtex
BibTex

1977

Books

titre
Quantum Mechanics
auteur
Claude Cohen-Tannoudji, Bernard Diu, Franck Laloë
article
Wiley, pp.1524, 1977
Accès au bibtex
BibTex

1975

Journal articles

titre
Very long 3He nuclear relaxation times at 4K using cryogenic coatings
auteur
René Barbé, Franck Laloë, Jean Brossel
article
Physical Review Letters, 1975, 34, pp.1488
Accès au bibtex
BibTex

1974

Journal articles

titre
Résonance magnétique en champ de radiofréquence inhomogène, Vérification expérimentale: mesure du coefficient de self diffusion de 3He
auteur
René Barbé, Michèle Leduc, Franck Laloë
article
Journal de Physique, 1974, 35, pp.935
Accès au bibtex
BibTex
titre
Résonance magnétique en champ de radiofréquence inhomogène - 2 e partie : Vérifications expérimentales ; mesure du coefficient de self-diffusion de 3He
auteur
René Barbé, M. Leduc, F. Laloë
article
Journal de Physique, 1974, 35 (12), pp.935-951. ⟨10.1051/jphys:019740035012093500⟩
resume
On vérifie en détail les calculs théoriques d'un article précédent sur les formes inhabituelles de courbes de résonance en champ de radiofréquence inhomogène. Les expériences sont réalisées sur du gaz de 3He orienté par pompage optique. Les différents effets prévus sont observés et étudiés (forme des deux courbes, large et étroite, différents types de déplacement des positions de la résonance, etc...). Ces expériences fournissent une mesure du coefficient de self-diffusion gazeux de 3He à 300 K : D33 = 1 440 ± 80 cm2 s-1 à 1 torr.
DOI
DOI : 10.1051/jphys:019740035012093500
Accès au texte intégral et bibtex
https://hal.science/jpa-00208218/file/ajp-jphys_1974_35_12_935_0.pdf BibTex
titre
Résonance magnétique en champ de radiofréquence inhomogène. 1 re partie : Étude théorique
auteur
René Barbé, M. Leduc, F. Laloë
article
Journal de Physique, 1974, 35 (10), pp.699-725. ⟨10.1051/jphys:019740035010069900⟩
resume
On étudie dans cet article l'effet d'un champ de radiofréquence très inhomogène sur un ensemble de spins en mouvement. Lorsque le champ magnétique statique est balayé au voisinage de la résonance, les variations de l'aimantation longitudinale globale des spins donnent des courbes de résonance nettement différentes des courbes habituelles ; elles sont en général la superposition de deux courbes de largeurs très différentes, la courbe large et la courbe fine. La forme de la première dépend essentiellement des caractéristiques du mouvement des atomes dans le champ de radiofréquence inhomogène. On étudie en détail le cas où ce mouvement est régi par un processus de diffusion : l'étude de la largeur à mi-hauteur de la courbe large donne alors le temps de diffusion des atomes dans la cellule, ce qui fournit un procédé commode de mesure des coefficients de diffusion dans les gaz. La courbe fine peut avoir, suivant les variations spatiales des inhomogénéités statique et de radiofréquence (et notamment suivant les corrélations entre les différentes composantes de ces inhomogénéités) des formes variées : elle peut être constituée d'une courbe d'absorption positive ou négative (aimantation minimale ou maximale à résonance), ou de la superposition d'une courbe d'absorption et d'une courbe de dispersion. De plus, des déplacements importants de la position de la résonance fine sont possibles, notamment sous l'effet de termes croisés entre inhomogénéités statiques et de radiofréquence.
DOI
DOI : 10.1051/jphys:019740035010069900
Accès au texte intégral et bibtex
https://hal.science/jpa-00208198/file/ajp-jphys_1974_35_10_699_0.pdf BibTex
titre
Résonance magnétique en champ de radiofréquence inhomogène”, Partie théorique
auteur
René Barbé, Michèle Leduc, Franck Laloë
article
Journal de Physique, 1974, 35, pp.699
Accès au bibtex
BibTex

1973

Journal articles

titre
Contribution à l'étude de l'échange de métastabilïté dans l'Hélium (1ère partie)
auteur
Jacques Dupont-Roc, Michèle Leduc, Franck Laloë
article
Journal de Physique, 1973, 34, pp.961
Accès au bibtex
BibTex
titre
Magnetic Resonance with Inhomogeneous R.F. Fields
auteur
René Barbé, Michèle Leduc, Franck Laloë
article
Lettere al Nuovo Cimento Della Societa Italiana di Fisica, 1973, 8, pp.915
Accès au bibtex
BibTex
titre
Contribution à l'étude du pompage optique par échange de métastabilité dans 3He. - Deuxième Partie
auteur
J. Dupont-Roc, M. Leduc, F. Laloë
article
Journal de Physique, 1973, 34 (11-12), pp.977-987. ⟨10.1051/jphys:019730034011-12097700⟩
resume
Dans ce second article, nous nous intéressons aux expériences de résonance magnétique sur des atomes de 3He soumis au pompage optique « indirect » par l'intermédiaire du niveau métastable 2 3S1. On calcule les caractéristiques des résonances dans le niveau fondamental et dans les deux sous-niveaux hyperfins du métastable 2 3S1. On utilise pour cela les résultats établis dans le premier article et relatifs aux collisions d'échange de métastabilité ; celles-ci introduisent en effet d'importants couplages entre les orientations des différents niveaux étudiés. On présente ensuite brièvement les expériences effectuées pour vérifier certains points de la théorie précédente, relatives aux largeurs, intensités et positions des courbes de résonance magnétique observées tant pour l'état fondamental que métastable.
DOI
DOI : 10.1051/jphys:019730034011-12097700
Accès au texte intégral et bibtex
https://hal.science/jpa-00208120/file/ajp-jphys_1973_34_11-12_977_0.pdf BibTex
titre
Contribution à l'étude du pompage optique par échange de métastabilité dans 3He. - Première Partie
auteur
J. Dupont-Roc, M. Leduc, F. Laloë
article
Journal de Physique, 1973, 34 (11-12), pp.961-976. ⟨10.1051/jphys:019730034011-12096100⟩
resume
On étudie théoriquement l'effet des collisions d'échange de métastabilité dans 3He sur les variables internes des atomes, dans l'état fondamental 1 1S0 et dans l'état métastable 2 3S 1. La méthode adoptée ici consiste à utiliser directement les équations qui régissent l'évolution de l'orientation et de l'alignement dans les différents niveaux. On parvient ainsi à une description théorique détaillée et relativement simple du mécanisme de pompage optique « indirect » de 3He. L'étude du couplage entre les orientations longitudinales des différents niveaux permet de rendre compte de la cinétique de ce pompage, en particulier du temps de construction de l'orientation nucléaire dans le niveau fondamental. En ce qui concerne les orientations transversales, on calcule en détail les effets de « circulation de cohérence », qui se traduisent par exemple par un déplacement des fréquences de résonance des différents niveaux.
DOI
DOI : 10.1051/jphys:019730034011-12096100
Accès au texte intégral et bibtex
https://hal.science/jpa-00208119/file/ajp-jphys_1973_34_11-12_961_0.pdf BibTex
titre
Contribution à l'étude de l'échange de métastabilïté dans l'Hélium (2ème partie)
auteur
Jacques Dupont-Roc, Michèle Leduc, Franck Laloë
article
Journal de Physique, 1973, 34, pp.977
Accès au bibtex
BibTex

Books

titre
Mécanique quantique
auteur
Claude Cohen-Tannoudji, Bernard Diu, Franck Laloë
article
Hermann, pp.1493, 1973
Accès au bibtex
BibTex

1972

Journal articles

titre
Orientation de niveaux excités du 21Ne par pompage optique dans une décharge
auteur
Alain Noël, Michèle Leduc, Franck Laloë
article
Comptes rendus hebdomadaires des séances de l’Académie des sciences. Série B, Sciences physiques, 1972, 274, pp.77
Accès au bibtex
BibTex
titre
Mesure du rapport entre les moments magnétiques du niveau 2 3s1 de 4He et du niveau fondamental de 3 He
auteur
M. Leduc, F. Laloë, J. Brossel
article
Journal de Physique, 1972, 33 (1), pp.49-58. ⟨10.1051/jphys:0197200330104900⟩
resume
On décrit dans cet article une expérience de pompage optique d'un mélange gazeux des deux isotopes 3He et 4He, dans lequel une décharge faible est entretenue. Ceci permet d'orienter simultanément le niveau métastable 2 3S1 de 4He et le niveau fondamental 1 1S0 de 3He, et de mesurer leurs fréquences de résonance respectives v J et vI dans un même champ magnétique. Après un grand nombre de vérifications destinées à éliminer les erreurs systématiques, cette expérience nous a permis de mesurer avec une grande précision le rapport des fréquences : [FORMULE]. On peut utiliser ce résultat, combiné avec un certain nombre de mesures antérieures, pour obtenir une nouvelle détermination du rapport des facteurs de Landé électroniques : [FORMULE]. Cette dernière valeur est en léger désaccord avec celle d'une mesure directe (mais moins précise) ainsi qu'avec une valeur théorique obtenues précédemment par d'autres auteurs.
DOI
DOI : 10.1051/jphys:0197200330104900
Accès au texte intégral et bibtex
https://hal.science/jpa-00207226/file/ajp-jphys_1972_33_1_49_0.pdf BibTex
titre
Dépolarisation du niveau métastable 23S1 de 4He par collisions quasi-résonnantes avec le néon; influence de la température
auteur
René Barbé, Michèle Leduc, Franck Laloë
article
Comptes rendus hebdomadaires des séances de l’Académie des sciences. Série B, Sciences physiques, 1972, 274, pp.645
Accès au bibtex
BibTex

1971

Journal articles

titre
Détection de l'orientation des ions 3He+ produite par pompage optique dans une décharge
auteur
Michèle Leduc, Franck Laloë
article
Optics Communications, 1971, 3, pp.56
Accès au bibtex
BibTex

1970

Journal articles

titre
Étude d'une nouvelle méthode permettant d'orienter, par pompage optique, des niveaux atomiques excités. Application à la mesure de la structure hyperfine de niveaux 1D de 3He
auteur
Milica Pavlović, Franck Laloë
article
Journal de Physique, 1970, 31 (2-3), pp.173-194. ⟨10.1051/jphys:01970003102-3017300⟩
resume
On expose dans cet article une nouvelle méthode permettant d'orienter des états atomiques excités ; cette méthode fait intervenir les trois processus suivants : — on crée par pompage optique une orientation nucléaire dans l'état fondamental des atomes d'une vapeur ; — une décharge H. F. porte les atomes dans divers états excités, sans détruire leur orientation nucléaire. — l'orientation nucléaire ainsi obtenue dans chaque niveau excité peut être transformée en orientation électronique, par l'intermédiaire du couplage hyperfin aI. J ; la lumière émise par la décharge est alors polarisée. L'étude théorique de l'orientation électronique obtenue par cette méthode a été effectuée, de façon à mettre en évidence l'influence des diverses caractéristiques du niveau excité, ainsi que celle du champ magnétique. Cette méthode a été utilisée pour orienter divers niveaux excités de 3He. Une étude détaillée a été effectuée pour les niveaux 3 1D, 4 1 D et 5 1D, notamment dans le cas où un champ magnétique statique introduit un découplage hyperfin partiel ; ces expériences ont conduit à une mesure de la structure hyperfine de ces trois niveaux.
DOI
DOI : 10.1051/jphys:01970003102-3017300
Accès au texte intégral et bibtex
https://hal.science/jpa-00206891/file/ajp-jphys_1970_31_2-3_173_0.pdf BibTex
titre
Pompage optique du 21Ne
auteur
Michèle Leduc, Franck Laloë, Jean Brossel
article
Comptes rendus hebdomadaires des séances de l’Académie des sciences. Série B, Sciences physiques, 1970, 271, pp.342
Accès au bibtex
BibTex
titre
Diverses résonances de croisement de niveaux sur des atomes pompés optiquement en champ nul. I. Théorie
auteur
C. Cohen-Tannoudji, J. Dupont-Roc, S. Haroche, F. Laloë
article
Revue de Physique Appliquée, 1970, 5 (1), pp.95-101. ⟨10.1051/rphysap:019700050109500⟩
resume
La lumière absorbée par une vapeur atomique soumise à un pompage optique transversal varie de manière résonnante lorsqu'on balaie le champ magnétique statique au voisinage du point de croisement en champ nul des sous-niveaux Zeeman de l'état fondamental (effet Hanle). Des résonances analogues apparaissent lorsqu'on effectue le pompage optique transversal de la vapeur atomique dans un champ modulé en amplitude (résonances paramétriques). La très grande finesse des raies ainsi observées sur les atomes alcalins les rend très intéressantes pour la détection et la mesure des champs magnétiques très faibles. On discute les propriétés de ces deux types de résonances et on met en évidence les avantages qu'il y a à utiliser les résonances paramétriques.
DOI
DOI : 10.1051/rphysap:019700050109500
Accès au texte intégral et bibtex
https://hal.science/jpa-00243381/file/ajp-rphysap_1970_5_1_95_0.pdf BibTex
titre
Diverses résonances de croisement de niveaux sur des atomes pompés optiquement en champ nul II. Applications à la mesure de champs faibles
auteur
C. Cohen-Tannoudji, J. Dupont-Roc, S. Haroche, F. Laloë
article
Revue de Physique Appliquée, 1970, 5 (1), pp.102-108. ⟨10.1051/rphysap:0197000501010200⟩
resume
On décrit la réalisation et les performances d'un magnétomètre utilisant les résonances de croisement de niveaux étudiées dans la communication précédente et observées sur une vapeur de 87Rb pompée optiquement. La très grande finesse des résonances (de l'ordre de 1 μG) permet la détection de champs très faibles, de l'ordre de 10-9 à 10-10 G avec une constante de temps de 3 s à la détection. On décrit également une expérience de détection à l'aide de ce magnétomètre du champ magnétique statique créé par des noyaux de 3He orientés en phase gazeuse.
DOI
DOI : 10.1051/rphysap:0197000501010200
Accès au texte intégral et bibtex
https://hal.science/jpa-00243340/file/ajp-rphysap_1970_5_1_102_0.pdf BibTex
titre
Etude d'une nouvelle méthode permettant d'orienter, par pompage optique, des états atomiques excités. Application à la mesure de la structure hyperfine de niveaux 1D de 3He
auteur
M. Pavlovic, Franck Laloë
article
Journal de Physique, 1970, 31, pp.173
Accès au bibtex
BibTex

Theses

titre
Etude des signaux de détection lumineuse dans une expérience de pompage optique. Orientation dans une décharge de niveaux atomiques excités.
auteur
Franck Laloë
article
Physique Atomique [physics.atom-ph]. Université Pierre et Marie Curie - Paris VI, 1970. Français. ⟨NNT : ⟩
resume
On étudie de façon générale les signaux de détection optique obtenus dans une expérience de pompage optique, avec l'aide de la matrice de polarisation et des techniques des opérateurs tensoriels irréductibles. Une méthode permettant d'orienter les niveaux atomiques excités créés dans une décharge est proposée et mise en oeuvre. Elle est appliquée à la mesure de la structure hyperfine de niveaux D dans l'Hélium trois.
Accès au texte intégral et bibtex
https://theses.hal.science/tel-00011581/file/1970-these-LALOE.pdf BibTex

1969

Journal articles

titre
Description d'une nouvelle méthode de mesure des structures hyperfines de niveaux atomiques excités ; application à certains niveaux 1D de 3He
auteur
M. Pavlovic, Franck Laloë
article
Comptes rendus hebdomadaires des séances de l’Académie des sciences. Série B, Sciences physiques, 1969, 268B, pp.1485
Accès au bibtex
BibTex
titre
Etude de l'influence du découplage hyperfin sur l'orientation et l'alignement électroniques obtenus, à partir d'une orientation nucléaire, dans divers niveaux excités de 3He
auteur
M. Pavlovic, Franck Laloë
article
Comptes rendus hebdomadaires des séances de l’Académie des sciences. Série B, Sciences physiques, 1969, 268B, pp.1436
Accès au bibtex
BibTex
titre
Relations entre l'état angulaire d'une vapeur atomique soumise au pompage optique et ses propriétés d'absorption et de dispersion - Seconde Partie
auteur
F. Laloë, M. Leduc, P. Minguzzi
article
Journal de Physique, 1969, 30 (4), pp.341-349. ⟨10.1051/jphys:01969003004034100⟩
resume
On étudie dans cet article le lien qui existe entre l'anisotropie des propriétés optiques d'une vapeur atomique et les propriétés angulaires des atomes dans l'état fondamental. La direction du faisceau lumineux qui se propage dans la vapeur, ainsi que l'orientation et l'alignement des atomes sont quelconques ; l'influence de chaque observable de l'état fondamental est discutée de manière détaillée à partir d'un modèle géométrique. Ce dernier fait intervenir d'une manière qui est précisée au cours de l'article un vecteur pour caractériser l'orientation, un ellipsoïde pour l'alignement. On retrouve ainsi un certain nombre de prévisions théoriques établies de manière différente dans un précédent article.
DOI
DOI : 10.1051/jphys:01969003004034100
Accès au texte intégral et bibtex
https://hal.science/jpa-00206792/file/ajp-jphys_1969_30_4_341_0.pdf BibTex
titre
Detection of the static field produced by oriented nuclei of optically pumped 3He gas
auteur
Claude Cohen-Tannoudji, Jacques Dupont-Roc, Serge Haroche, Franck Laloë
article
Physical Review Letters, 1969, 22, pp.758
Accès au bibtex
BibTex
titre
Relations entre l'état angulaire d'une vapeur atomique soumise au pompage optique et ses propriétés d'absorption et de dispersion. - Première Partie
auteur
F. Laloë, M. Leduc, P. Minguzzi
article
Journal de Physique, 1969, 30 (2-3), pp.277-288. ⟨10.1051/jphys:01969003002-3027700⟩
resume
Cet article est consacré à l'étude de l'optimisation des signaux de détection optique obtenus dans une expérience de pompage optique. Les formules générales obtenues dans des publications antérieures sont explicitées en fonction des divers paramètres intervenant dans une expérience : direction de propagation du faisceau lumineux, composition spectrale, nature du polariseur et de l'analyseur ; on peut ainsi déterminer dans chaque cas particulier le montage qui permet de détecter dans les meilleures conditions les observables atomiques auxquelles on s'intéresse. Les calculs exposés font intervenir le formalisme des opérateurs tensoriels irréductibles. Dans un second article, nous montrerons comment les résultats obtenus de cette manière peuvent être établis à partir de considérations générales purement géométriques.
DOI
DOI : 10.1051/jphys:01969003002-3027700
Accès au texte intégral et bibtex
https://hal.science/jpa-00206785/file/ajp-jphys_1969_30_2-3_277_0.pdf BibTex

1968

Journal articles

titre
Etude de l'influence des caractéristiques d'un faisceau lumineux détecteur sur les signaux d'absorption et de dispersion modulée d'une vapeur de 201Hg
auteur
Franck Laloë, Michèle Leduc, Paolo Minguzzi
article
Comptes rendus hebdomadaires des séances de l’Académie des sciences. Série B, Sciences physiques, 1968, 267B, pp.328
Accès au bibtex
BibTex
titre
Etude d'une nouvelle méthode permettant d'orienter et d'aligner les divers niveaux excités de 3He
auteur
Franck Laloë
article
Comptes rendus hebdomadaires des séances de l’Académie des sciences. Série B, Sciences physiques, 1968, 267B, pp.208
Accès au bibtex
BibTex
titre
Etude de l'influence sur les propriétés de dispersion et d'absorption d'une vapeur de 201Hg, des modulations de l'orientation et de l'alignement dans l'état fondamental des atomes
auteur
Franck Laloë, Michèle Leduc, Paolo Minguzzi
article
Comptes rendus hebdomadaires des séances de l’Académie des sciences. Série B, Sciences physiques, 1968, 266B, pp.1517
Accès au bibtex
BibTex

1967

Journal articles

titre
Modification de la matrice polarisation d'un faisceau lumineux lors de la traversée d'une vapeur atomique soumise au pompage optique. - Deuxième Partie
auteur
C. Cohen-Tannoudji, F. Laloë
article
Journal de Physique, 1967, 28 (8-9), pp.722-734. ⟨10.1051/jphys:01967002808-9072200⟩
resume
Les formules générales obtenues dans un précédent article sont appliquées à un certain nombre de cas particuliers : isotopes impairs et isotopes pairs du mercure, alcalins. Dans le cas des isotopes impairs du mercure, on souligne l'analogie étroite entre l'équation qui donne la modification de polarisation lumineuse et celle qui décrit l'évolution de la matrice densité atomique σf. On étudie de façon détaillée le lien qui existe entre les propriétés de symétrie de σf et les « polarisations principales » de la vapeur. Dans le cas des isotopes pairs du mercure, on étudie l'effet d'un champ statique et d'un champ de radiofréquence sur la lumière transmise. Enfin, dans le cas des alcalins, on met en évidence des effets nouveaux liés à l'existence de « cohérences hyperfines ».
DOI
DOI : 10.1051/jphys:01967002808-9072200
Accès au texte intégral et bibtex
https://hal.science/jpa-00206573/file/ajp-jphys_1967_28_8-9_722_0.pdf BibTex
titre
Mise en évidence d'une orientation électronique dans les états excités de 3He obtenue à partir d'une orientation nucléaire dans l'état fondamental
auteur
Françoise Grossetête, Franck Laloë, Claude Cohen-Tannoudji, Jean Brossel
article
Comptes rendus hebdomadaires des séances de l’Académie des sciences. Série B, Sciences physiques, 1967, 265B, pp.1247
Accès au bibtex
BibTex
titre
Modification de la matrice polarisation d'un faisceau lumineux lors de la traversée d'une vapeur atomique soumise au pompage optique. - Première Partie
auteur
C. Cohen-Tannoudji, F. Laloë
article
Journal de Physique, 1967, 28 (7), pp.505-513. ⟨10.1051/jphys:01967002807050500⟩
resume
On étudie la propagation d'un faisceau lumineux dans une vapeur où les atomes subissent une résonance magnétique et sont décrits dans l'état fondamental par une matrice densité quelconque σf(r, t), dépendant éventuellement de r. La polarisation de l'onde électromagnétique est caractérisée par une matrice π d'ordre deux dont on rappelle la définition et quelques propriétés. On calcule la différence πT — π I entre la polarisation du faisceau transmis et celle du faisceau incident. On trouve qu'en général πT — πI dépend non seulement des « populations » des sous-niveaux de l'état fondamental, mais encore des « cohérences hertziennes » entre ces sous-niveaux. Dans un second article, les formules générales obtenues seront appliquées à un certain nombre de cas particuliers intéressants.
DOI
DOI : 10.1051/jphys:01967002807050500
Accès au texte intégral et bibtex
https://hal.science/jpa-00206546/file/ajp-jphys_1967_28_7_505_0.pdf BibTex