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SUMMARY:High order correlations and what we can learn about the solution f
 or many body problems from experiment - Jörg Schmiedmayer (Technische Uni
 versität Wien)
DTSTART:20160114T113000Z
DTEND:20160114T123000Z
UID:TALK64632@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:The knowledge of all correlation functions of a system is equi
 valent to solving the corresponding quantum many-body problem. If one can 
 identify the relevant degrees of freedom\, the knowledge of a finite set o
 f correlation functions is in many cases sufficient to determine a suffici
 ently accurate solution of the corresponding field theory. Complete factor
 ization is equivalent to identifying the relevant degrees of freedom where
  the Hamiltonian becomes diagonal. I will give examples how one can apply 
 this powerful theoretical concept in experiment.  <br><span><br>A detailed
  study of non-translation invariant correlation functions reveals that the
  pre-thermalized state a system of two 1-dimensional quantum gas relaxes t
 o after a splitting quench [1]\, is described by a generalized Gibbs ensem
 ble [2]. This is verified through phase correlations up to 10th order.</sp
 an>  <br><br>Interference in a pair of tunnel-coupled one-dimensional atom
 ic super-fluids\, which realize the quantum Sine-Gordon / massive Thirring
  models\, allows us to study if\, and under which conditions the higher co
 rrelation functions factorize [3]. This allowed us to characterize the ess
 ential features of the model solely from our experimental measurements: de
 tecting the relevant quasi-particles\, their interactions and the differen
 t topologically distinct vacuum-states the quasi-particles live in. The ex
 periment thus provides a comprehensive insights into the components needed
  to solve a non-trivial quantum field theory.  <br><br>Our examples establ
 ish a general method to analyse quantum systems through experiments. It th
 us represents a crucial ingredient towards the implementation and verifica
 tion of quantum simulators.  <br><span><br>Work performed in collaboration
  with E.Demler (Harvard)\, Th. Gasenzer und J. Berges (Heidelberg). Suppor
 ted by the Wittgenstein Prize\, the Austrian Science Foundation (FWF): SFB
  FoQuS: F40-P10 and the EU: ERC-AdG <i>QuantumRelax</i></span>  <br><span>
 <br>[1] M. Gring et al.\, Science\, <b>337\, </b>1318 (2012)\; </span>  <s
 pan>[2] <span>T. Langen et al.\, Science <b>348</b> 207-211 (2015).</span>
 </span>  [3] T. Schweigler et al.\, arXiv:1505.03126
LOCATION:Seminar Room 1\, Newton Institute
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