QxSQA: GPGPU-Accelerated Simulated Quantum Annealer within a Non-Linear Optimization and Boltzmann Sampling Framework

We introduce QxSQA, a GPGPU-Accelerated Simulated Quantum Annealer based on Path-Integral Monte Carlo (PIMC). QxSQA is tuned for finding low-energy solutions to integer, non-linear optimization problems of up to 214 (16,384) binary variables with quadratic interactions on a single GPU instance. Experimental results demonstrate QxSQA can solve Maximum Clique test problems of 8,100 binary variables with planted solutions in under one minute, with linear scaling against key optimization parameters on other large-scale problems. Through the PIMC formulation, QxSQA also functions as an accurate sampler of Boltzmann distributions for machine learning applications. Experimental characterization of Boltzmann sampling results for a reinforcement learning problem showed good convergence performance at useful scales. Our implementation integrates as a solver within our QxBranch developer platform, positioning developers to efficiently develop applications using QxSQA, and then test the same application code on a quantum annealer or universal quantum computer hardware platform such as those from D-Wave Systems, IBM, or Rigetti Computing.