We investigate alternative annealing schedules on the current generation of
quantum annealing hardware (the D-Wave 2000Q), which includes the use of
forward and reverse annealing with an intermediate pause. This work provides
new insights into the inner workings of these devices (and quantum devices in
general), particular into how thermal effects govern the system dynamics. We
show that a pause mid-way through the anneal can cause a dramatic change in the
output distribution, and we provide evidence suggesting thermalization is
indeed occurring during such a pause. We demonstrate that upon pausing the
system in a narrow region shortly after the minimum gap, the probability of
successfully finding the ground state of the problem Hamiltonian can be
increased over an order of magnitude. We relate this effect to relaxation (i.e.
thermalization) after diabatic and thermal excitations that occur in the region
near to the minimum gap. For a set of large-scale problems of up to 500 qubits,
we demonstrate that the distribution returned from the annealer very closely
matches a (classical) Boltzmann distribution of the problem Hamiltonian, albeit
one with a temperature at least 1.5 times higher than the (effective)
temperature of the annealer. Moreover, we show that larger problems are more
likely to thermalize to a classical Boltzmann distribution.

我们在当前的量子退火硬件（D-Wave 2000Q）上研究了一些替代的退火计划，并在间歇期间使用前向和反向退火，提供了关于这些设备内部运行方式的新见解，特别是关于热效应如何支配系统动力学的信息。