QuBRIM: A CMOS Compatible Resistively-coupled Ising Machine with Quantized Nodal Interactions

Physical Ising machines have been shown to solve combinatoric optimization problems with orders-of-magnitude improvements in speed and energy efficiency over v on Neumann systems. However, building such a system is still in its infancy and a scalable, robust implementation remains challenging. CMOS- compatible electronic Ising machines (e.g., [1]) are promising as the mature technology helps bring scale, speed, and energy efficiency to the dynamical system. However, subtle issues can arise when using voltage-controlled transistors to act as programmable resistive coupling. In this paper, we propose a version of resistively-coupled Ising machine using quantized nodal interactions (QuBRIM), which significantly improved the predictability of the coupling resistor. The functionality of QuBRIM is demonstrated by solving the well-known Max-Cut problem using both behavioral and circuit level simulations in 45 nm CMOS technology node. We show that the dynamical system naturally seeks local minima in the objective function's energy landscape and that by applying spin-fix annealing, the system reaches a global minimum with a high probability.