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CATEGORIES:CQIF Seminar
SUMMARY:Quantum annealing on Ising spin glasses - Troels F
rimodt Rønnow (NRC Cambridge)
DTSTART;TZID=Europe/London:20141121T120000
DTEND;TZID=Europe/London:20141121T130000
UID:TALK56373AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/56373
DESCRIPTION:While a universal quantum computing is not yet wit
hin our reach\, quantum computing technology has m
atured to the point where certain quantum algorith
ms and simulators can be realized in laboratories.
One example of this is quantum annealing which is
realized in D-Wave One and Two. In this talk\, we
review some aspects of the recent development of
quantum annealing with focus on D-Wave One and Two
. First we discuss various models which potentiall
y could explain the behaviour of D-Wave (DW) machi
nes and we demonstrate that the statistics of DW a
re well explained using path-integral quantum Mont
e Carlo quantum annealing (SQA). Next\, we look a
t the scaling of DW and compare this to simulated
thermal annealing (SA). For the chosen problems\,
we show that SA is always superior to DW when look
ing at the scaling\, and that the two approaches a
re about equally fast if one looks at total time t
o solution. That SA should scale better than SQA/D
W is in contrast to a theory formulated in 2002 wh
ere it was shown that SQA is more efficient than S
A in finding low-energy states. To resolve this di
screpancy we revisit the work by Santoro. Studying
thousands of problems\, we show the better scalin
g report by Santoro et al. is a result of certain
assumptions in the derivation of SQA. The conseque
nce of these assumptions is that the theory does n
ot apply to physical systems\, and in particular n
ot to DW. To further support the claim that SQA sh
ould scale worse than SA\, we look at the distribu
tions of time-to-solution. We demonstrate that the
SQA distributions are dominated by long fat tails
. In turn\, this means that the mean time-to-solut
ion for a large problem set is expected to be wors
e for SQA than SA. Finally\, we discuss some of th
e open questions.
LOCATION:MR13\, Centre for Mathematical Sciences\, Wilberf
orce Road\, Cambridge
CONTACT:Sergii Strelchuk
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