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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:High order correlations and what we can learn abou
t the solution for many body problems from experim
ent - Jörg Schmiedmayer (Technische Universität Wi
en)
DTSTART;TZID=Europe/London:20160114T113000
DTEND;TZID=Europe/London:20160114T123000
UID:TALK64632AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/64632
DESCRIPTION:The knowledge of all correlation functions of a sy
stem is equivalent to solving the corresponding qu
antum many-body problem. If one can identify the r
elevant degrees of freedom\, the knowledge of a fi
nite set of correlation functions is in many cases
sufficient to determine a sufficiently accurate s
olution of the corresponding field theory. Complet
e factorization is equivalent to identifying the r
elevant degrees of freedom where the Hamiltonian b
ecomes diagonal. I will give examples how one can
apply this powerful theoretical concept in experim
ent.

A detailed study of non-transl
ation invariant correlation functions reveals that
the pre-thermalized state a system of two 1-dimen
sional quantum gas relaxes to after a splitting qu
ench [1]\, is described by a generalized Gibbs ens
emble [2]. This is verified through phase correlat
ions up to 10th order.

Interferenc
e in a pair of tunnel-coupled one-dimensional atom
ic super-fluids\, which realize the quantum Sine-G
ordon / massive Thirring models\, allows us to stu
dy if\, and under which conditions the higher corr
elation functions factorize [3]. This allowed us t
o characterize the essential features of the model
solely from our experimental measurements: detect
ing the relevant quasi-particles\, their interacti
ons and the different topologically distinct vacuu
m-states the quasi-particles live in. The experime
nt thus provides a comprehensive insights into the
components needed to solve a non-trivial quantum
field theory.

Our examples establish a ge
neral method to analyse quantum systems through ex
periments. It thus represents a crucial ingredient
towards the implementation and verification of qu
antum simulators.

Work performed in
collaboration with E.Demler (Harvard)\, Th. Gasen
zer und J. Berges (Heidelberg). Supported by the W
ittgenstein Prize\, the Austrian Science Foundatio
n (FWF): SFB FoQuS: F40-P10 and the EU: ERC-AdG *QuantumRelax*

[1] M. Gri
ng et al.\, Science\, **337\, **1318 (2012)\; <
/span> [2] T. Langen et al.\, Science
**348** 207-211 (2015). [3] T.
Schweigler et al.\, arXiv:1505.03126
LOCATION:Seminar Room 1\, Newton Institute
CONTACT:INI IT
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