# Annealing by simulating the coherent Ising machine

## TL;DR

This paper introduces a classical simulation method for the coherent Ising machine that surpasses the physical CIM in speed and quality, and can handle arbitrary coupling strengths, potentially inspiring new quantum-inspired algorithms.

## Contribution

A novel classical simulation approach for the CIM that outperforms the physical device and noisy mean-field annealer, capable of handling arbitrary real-valued couplings.

## Key findings

- Classical simulation outperforms physical CIM in quality and speed.
- Simulation handles arbitrary real-valued node couplings.
- Results suggest potential for new quantum-inspired classical algorithms.

## Abstract

The coherent Ising machine (CIM) enables efficient sampling of low-lying energy states of the Ising Hamiltonian with all-to-all connectivity by encoding the spins in the amplitudes of pulsed modes in an optical parametric oscillator (OPO). The interaction between the pulses is realized by means of measurement-based optoelectronic feedforward which enhances the gain for lower-energy spin configurations. We present an efficient method of simulating the CIM on a classical computer that outperforms the CIM itself as well as the noisy mean-field annealer in terms of both the quality of the samples and the computational speed. It is furthermore advantageous with respect to the CIM in that it can handle Ising Hamiltonians with arbitrary real-valued node coupling strengths. These results illuminate the nature of the faster performance exhibited by the CIM and may give rise to a new class of quantum-inspired algorithms of classical annealing that can successfully compete with existing methods.