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TZID:Europe/Paris
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BEGIN:VEVENT
UID:0-599@lptms.universite-paris-saclay.fr
DTSTART:20180412T113000Z
DTEND:20180412T120000Z
DTSTAMP:20180321T213517Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/seminaire-du-lptm
s-gregoire-ithier-seminaire-exceptionnel/
SUMMARY:Séminaire du LPTMS: Grégoire Ithier *** séminaire exceptionnel *
** - LPTMS\, salle 201\, 2ème étage\, Bât 100\, Campus d'Orsay - 12 Avr
18 11:30
DESCRIPTION:Typicality and unconventional equilibrium states of an embedded
quantum system.\nGrégoire Ithier (Royal Holloway\, London\, UK)\n\nIn re
cent years\, the progress in quantum engineering has provided new tools fo
r simulating the dynamics of truly isolated quantum systems. These systems
\, made of trapped ions or cold atoms[1]\, can be prepared in a global pur
e state and their level of isolation is such that they evolve unitarily ac
cording to the Schrödinger equation. Surprisingly\, despite being at all
times in a pure quantum state\, they display signatures of a local equilib
ration which can be in strong disagreement with the predictions of statis
tical physics [2]. These experimental facts are clearly questioning what k
ind of statistical description is relevant for isolated many body quantum
systems.\n\nIn this talk\, I will present our recent results on a theoreti
cal model dedicated to this problem. This model considers a quantum system
coupled to a large quantum environment\, and introduces some randomness
at the level of the interaction Hamiltonian. We then demonstrate that the
system has a typical dynamics for several classes of random interactions
and most importantly for arbitrary system\, environment\, and global initi
al state [3]. In other words\, the microscopic structure of interaction Ha
miltonians does not matter and reduced density matrices have a self-averag
ing property. \n\nThese results have two important consequences: first th
ey can explain the absence of sensitivity to microscopic details of proces
ses like e.g. thermalization. Second they provide the rigorous ground for
an averaging procedure over random interactions which can be used for anal
ytical non perturbative calculations performed with full generality i.e. f
or arbitrary system\, environment\, and initial state.\n\nWe apply this te
chnique to calculate analytically the stationary state at long times of th
e system and find a new thermodynamical ensemble more general than the mic
rocanonical one [4]. \n \n\n [1] C. Gross and I. Bloch\, Quantum simula
tions with ultracold atoms in optical lattices\, Science 357\, 6355\, pp.
995-1001 (2017)\n [2] M. Schreiber et al\, Observation of many-body loc
alization of interacting fermions in a quasirandom optical lattice\, Scien
ce 349\, 6250\, pp. 842-845 (2015)\n [3] G. Ithier and F. Benaych-Georges
\, Dynamical typicality of embedded quantum systems\, Phys. Rev. A 96\, 01
2108 (2017)\n [4] G. Ithier\, S. Ascroft\, and F. Benaych-Georges\, Typic
al equilibrium state of an embedded quantum system\, Phys. Rev. E 96\, 060
102(R) (2017) \n\n\n
LOCATION:LPTMS\, salle 201\, 2ème étage\, Bât 100\, Campus d'Orsay\, 15
Rue Georges Clemenceau\, Orsay\, 91405\, France
GEO:48.698185;2.181768
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=15 Rue Georges Clemenceau\,
Orsay\, 91405\, France;X-APPLE-RADIUS=100;X-TITLE=LPTMS\, salle 201\, 2è
me étage\, Bât 100\, Campus d'Orsay:geo:48.698185,2.181768
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