Testing a quantum annealer as a quantum thermal sampler
Abstract
Motivated by two recent experiments in which thermal properties of complex manybody systems were successfully reproduced on a commercially available quantum annealer, we examine the extent to which quantum annealing hardware can reliably sample from the thermal state associated with a target quantum Hamiltonian. We address this question by studying the thermal properties of the canonical onedimensional transversefield Ising model on a DWave 2000Q quantum annealing processor. We find that the quantum processor fails to produce the correct expectation values predicted by Quantum Monte Carlo. Comparing to master equation simulations, we find that this discrepancy is best explained by how the measurements at finite transverse fields are enacted on the device. Specifically, measurements at finite transverse field require the system to be quenched from the target Hamiltonian to a Hamiltonian with negligible transverse field, and this quench is too slow. We elaborate on how the limitations imposed by such hardware make it an unlikely candidate for studying the thermal properties of generic quantum manybody systems.
 Publication:

arXiv eprints
 Pub Date:
 February 2020
 arXiv:
 arXiv:2003.00361
 Bibcode:
 2020arXiv200300361G
 Keywords:

 Quantum Physics
 EPrint:
 12 pages, 13 figures