Assessing the Quantum in Quantum Annealing

Annealing is a general purpose computational strategy which endeavors to harness fluctuations to solve sampling problems. A drawback of this approach is that it is difficult to program an annealer to sample from a user specified distribution. Quantum annealing (QA) utilizes quantum effects to drive fluctuations and thus can potentially sample from specific distributions with an algorithmic speedup. A crucial element of understanding QA is to clearly delineate fluctuations that arise from quantum effects from those that arise from non-quantum effects such as thermal fluctuations. Our approach to this problem utilizes the theory of quantum distributions on phase space and focuses on the specific non-linear dynamics that arise in Josephson junction circuits. By comparing quantum and classical dynamics, we are able to pinpoint the role that quantum effects play.