4,096 research outputs found
Quantum Annealing and Analog Quantum Computation
We review here the recent success in quantum annealing, i.e., optimization of
the cost or energy functions of complex systems utilizing quantum fluctuations.
The concept is introduced in successive steps through the studies of mapping of
such computationally hard problems to the classical spin glass problems. The
quantum spin glass problems arise with the introduction of quantum
fluctuations, and the annealing behavior of the systems as these fluctuations
are reduced slowly to zero. This provides a general framework for realizing
analog quantum computation.Comment: 22 pages, 7 figs (color online); new References Added. Reviews of
Modern Physics (in press
Quantum Annealing - Foundations and Frontiers
We briefly review various computational methods for the solution of
optimization problems. First, several classical methods such as Metropolis
algorithm and simulated annealing are discussed. We continue with a description
of quantum methods, namely adiabatic quantum computation and quantum annealing.
Next, the new D-Wave computer and the recent progress in the field claimed by
the D-Wave group are discussed. We present a set of criteria which could help
in testing the quantum features of these computers. We conclude with a list of
considerations with regard to future research.Comment: 22 pages, 6 figures. EPJ-ST Discussion and Debate Issue: Quantum
Annealing: The fastest route to large scale quantum computation?, Eds. A.
Das, S. Suzuki (2014
Relation between quantum fluctuations and the performance enhancement of quantum annealing in a nonstoquastic Hamiltonian
We study the relation between quantum fluctuations and the significant
enhancement of the performance of quantum annealing in a mean-field
Hamiltonian. First-order quantum phase transitions were shown to be reduced to
second order by antiferromagnetic transverse interactions in a mean-field-type
many-body-interacting Ising spin system in a transverse field, which means an
exponential speedup of quantum annealing by adiabatic quantum computation. We
investigate if and how quantum effects manifest themselves around these first-
and second-order phase transitions to understand if the antiferromagnetic
transverse interactions appended to the conventional transverse-field Ising
model induce notable quantum effects. By measuring the proximity of the
semiclassical spin-coherent state to the true ground state as well as the
magnitude of the concurrence representing entanglement, we conclude that
significant quantum fluctuations exist around second-order transitions, whereas
quantum effects are much less prominent at first-order transitions. Although
the location of the transition point can be predicted by the classical picture,
system properties near the transition need quantum-mechanical descriptions for
a second-order transition but not necessarily for first order. It is also found
that quantum fluctuations are large within the ferromagnetic phase after a
second-order transition from the paramagnetic phase. These results suggest that
the antiferromagnetic transverse interactions induce marked quantum effects,
and this fact would be related to closely to the significant enhancement of the
performance of quantum annealing.Comment: 9 pages, 8 figure
An Overview of Approaches to Modernize Quantum Annealing Using Local Searches
I describe how real quantum annealers may be used to perform local (in state
space) searches around specified states, rather than the global searches
traditionally implemented in the quantum annealing algorithm. The quantum
annealing algorithm is an analogue of simulated annealing, a classical
numerical technique which is now obsolete. Hence, I explore strategies to use
an annealer in a way which takes advantage of modern classical optimization
algorithms, and additionally should be less sensitive to problem
mis-specification then the traditional quantum annealing algorithm.Comment: In Proceedings PC 2016, arXiv:1606.06513. An extended version of this
contribution will appear on arXiv soon which will describe more detailed
algorithms, comment more on robustness to problem mis-specification, comment
on thermal sampling applications, and discuss applications on real device
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