Time-Division Multiplexing Ising Computer Using Single Stochastic Magnetic Tunneling Junction

Abstract

A magnetic tunneling junction (MTJ) with very low energy barrier, which shows controllable stochastic property, is recently proposed to constitute the probability bit (P-Bit). With the P-Bit, Ising computation, which is a general and powerful computing platform for both conventional and non-conventional problems, is implemented. However, such hardware emulation suffers from the severe intrinsic variations of a stochastic MTJ device. The nonuniform probability switching curves of different stochastic MTJs hinder straightforward expansion of Ising computer to a large P-Bits array for solving more complicated problems. In this work, we propose a novel Ising computer using a single stochastic MTJ device. With the utilization of the time-division multiplexing (TDM) technology, a “Compute–Read–Switch” scheme is proposed, so that the single stochastic MTJ can act as multiple P-Bits during Ising computation. A design guide for the current magnitude and time duration of the “Compute–Read–Switch” scheme is investigated and provided. Furthermore, NOT and XOR logic gates are implemented with our proposal. An accuracy rate as high as 69% for the integer factorization is also achieved, which is comparable with conventional Ising computer. Meanwhile, the TDM Ising computer avoids the calibration process, which is mandatory in the conventional Ising computer.