Ising Machine Based on Electrically Coupled Spin Hall Nano-Oscillators

TL;DR

This paper proposes a spin Hall nano-oscillator network as an efficient, programmable, and scalable hardware platform for Ising machines, enabling faster and more energy-efficient solutions to complex optimization problems.

Contribution

It introduces an analytical framework and a circuit-level model for electrically coupled spin Hall nano-oscillators, facilitating their use in practical Ising machine implementations.

Findings

Analytical model links oscillator properties to Ising model

Verilog-A device enables circuit simulation of oscillator networks

Performance analysis shows potential for CMOS integration

Abstract

The Ising machine is an unconventional computing architecture that can be used to solve NP-hard combinatorial optimization problems more efficiently than traditional von Neumann architectures. Fast, compact oscillator networks which provide programmable connectivities among arbitrary pairs of nodes are highly desirable for the development of practical oscillator-based Ising machines. Here we propose using an electrically coupled array of GHz spin Hall nano-oscillators to realize such a network. By developing a general analytical framework that describes injection locking of spin Hall oscillators with large precession angles, we explicitly show the mapping between the coupled oscillators' properties and the Ising model. We integrate our analytical model into a versatile Verilog-A device that can emulate the coupled dynamics of spin Hall oscillators in circuit simulators. With this abstract model, we analyze the performance of the spin Hall oscillator network at the circuit level using conventional electronic components and considering phase noise and scalability. Our results provide design insights and analysis tools toward the realization of a CMOS-integrated spin Hall oscillator Ising machine operating with a high degree of time, space, and energy efficiency.