02028nas a2200229 4500008004100000245008700041210006900128260001300197300001400210490000800224520134100232100002101573700001901594700001501613700001901628700001701647700002301664700002501687700002501712700002401737856003701761 2014 eng d00aNon-local propagation of correlations in long-range interacting quantum systems
0 aNonlocal propagation of correlations in longrange interacting qu c2014/7/9 a198 - 2010 v5113 a The maximum speed with which information can propagate in a quantum many-body
system directly affects how quickly disparate parts of the system can become
correlated and how difficult the system will be to describe numerically. For
systems with only short-range interactions, Lieb and Robinson derived a
constant-velocity bound that limits correlations to within a linear effective
light cone. However, little is known about the propagation speed in systems
with long-range interactions, since the best long-range bound is too loose to
give the correct light-cone shape for any known spin model and since analytic
solutions rarely exist. In this work, we experimentally determine the spatial
and time-dependent correlations of a far-from-equilibrium quantum many-body
system evolving under a long-range Ising- or XY-model Hamiltonian. For several
different interaction ranges, we extract the shape of the light cone and
measure the velocity with which correlations propagate through the system. In
many cases we find increasing propagation velocities, which violate the
Lieb-Robinson prediction, and in one instance cannot be explained by any
existing theory. Our results demonstrate that even modestly-sized quantum
simulators are well-poised for studying complicated many-body systems that are
intractable to classical computation.
1 aRicherme, Philip1 aGong, Zhe-Xuan1 aLee, Aaron1 aSenko, Crystal1 aSmith, Jacob1 aFoss-Feig, Michael1 aMichalakis, Spyridon1 aGorshkov, Alexey, V.1 aMonroe, Christopher uhttp://arxiv.org/abs/1401.5088v101243nas a2200181 4500008004100000245012700041210006900168260001400237490000700251520064800258100002100906700001900927700001700946700001500963700002200978700002401000856003701024 2013 eng d00aExperimental Performance of a Quantum Simulator: Optimizing Adiabatic Evolution and Identifying Many-Body Ground States
0 aExperimental Performance of a Quantum Simulator Optimizing Adiab c2013/7/310 v883 a We use local adiabatic evolution to experimentally create and determine the
ground state spin ordering of a fully-connected Ising model with up to 14
spins. Local adiabatic evolution -- in which the system evolution rate is a
function of the instantaneous energy gap -- is found to maximize the ground
state probability compared with other adiabatic methods while only requiring
knowledge of the lowest $\sim N$ of the $2^N$ Hamiltonian eigenvalues. We also
demonstrate that the ground state ordering can be experimentally identified as
the most probable of all possible spin configurations, even when the evolution
is highly non-adiabatic.
1 aRicherme, Philip1 aSenko, Crystal1 aSmith, Jacob1 aLee, Aaron1 aKorenblit, Simcha1 aMonroe, Christopher uhttp://arxiv.org/abs/1305.2253v101289nas a2200205 4500008004100000245007500041210006900116260001300185490000800198520067800206100002100884700001900905700002200924700001700946700001500963700001900978700002500997700002401022856003701046 2013 eng d00aQuantum Catalysis of Magnetic Phase Transitions in a Quantum Simulator0 aQuantum Catalysis of Magnetic Phase Transitions in a Quantum Sim c2013/9/50 v1113 a We control quantum fluctuations to create the ground state magnetic phases of
a classical Ising model with a tunable longitudinal magnetic field using a
system of 6 to 10 atomic ion spins. Due to the long-range Ising interactions,
the various ground state spin configurations are separated by multiple
first-order phase transitions, which in our zero temperature system cannot be
driven by thermal fluctuations. We instead use a transverse magnetic field as a
quantum catalyst to observe the first steps of the complete fractal devil's
staircase, which emerges in the thermodynamic limit and can be mapped to a
large number of many-body and energy-optimization problems.
1 aRicherme, Philip1 aSenko, Crystal1 aKorenblit, Simcha1 aSmith, Jacob1 aLee, Aaron1 aIslam, Rajibul1 aCampbell, Wesley, C.1 aMonroe, Christopher uhttp://arxiv.org/abs/1303.6983v2