Theoretische Physik, ETH Zurich, 8093 Zurich, Switzerland.
Google, Brandschenkestrasse 110, 8002 Zurich, Switzerland.
Science. 2015 Apr 10;348(6231):215-7. doi: 10.1126/science.aaa4170. Epub 2015 Mar 12.
Quantum annealers use quantum fluctuations to escape local minima and find low-energy configurations of a physical system. Strong evidence for superiority of quantum annealing (QA) has come from comparing QA implemented through quantum Monte Carlo (QMC) simulations to classical annealing. Motivated by recent experiments, we revisit the question of when quantum speedup may be expected. Although a better scaling is seen for QA in two-dimensional Ising spin glasses, this advantage is due to time discretization artifacts and measurements that are not possible on a physical quantum annealer. Simulations in the physically relevant continuous time limit, on the other hand, do not show superiority. Our results imply that care must be taken when using QMC simulations to assess the potential for quantum speedup.
量子退火器利用量子涨落来摆脱局部最小值，并找到物理系统的低能构型。通过量子蒙特卡罗（QMC）模拟与经典退火进行比较，为量子退火（QA）的优越性提供了强有力的证据。受最近实验的启发，我们重新审视了何时可以预期量子加速的问题。尽管在二维伊辛自旋玻璃中，QA 的扩展情况更好，但这种优势归因于时间离散化的伪影和物理量子退火器上不可能进行的测量。另一方面，在物理上相关的连续时间限制下的模拟则没有显示出优势。我们的结果表明，在使用 QMC 模拟来评估量子加速的潜力时，必须小心谨慎。
