UC Santa Barbara

The growing field of quantum computing is based on the concept of a q-bit, which is a delicate superposition of 0 and 1, requiring cryogenic temperatures for its physical realization along with challenging coherent coupling techniques for entangling them. By contrast, a probabilistic bit or a p-bit is a robust classical entity that fluctuates between 0 and 1 and can be implemented at room temperature using present-day technology. Here, we show that a probabilistic coprocessor built out of room-temperature p-bits can be used to accelerate simulations of a special class of quantum many-body systems that are sign-problem-free or "stoquastic," leveraging the well-known Suzuki-Trotter decomposition that maps a d-dimensional quantum many-body Hamiltonian to a d+1-dimensional classical Hamiltonian. This mapping allows an efficient emulation of a quantum system by classical computers and is commonly used in software to perform quantum Monte Carlo (QMC) algorithms. By contrast, we show that a compact, embedded magnetic tunnel junction (MTJ)-based coprocessor can serve as a highly efficient hardware accelerator for such QMC algorithms, providing an improvement in speed of several orders of magnitude compared to optimized CPU implementations. Using realistic device-level spice simulations, we demonstrate that the correct quantum correlations can be obtained using a classical p-circuit built with existing technology and operating at room temperature. The proposed coprocessor can serve as a tool to study stoquastic quantum many-body systems, overcoming challenges associated with physical quantum annealers.