Scientists from the NTT Research Physics & Informatics (PHI) Lab and Tokyo Institute of Technology (Tokyo Tech) have presented a new algorithm that successfully combines amplitude control feedback and Zeeman terms to overcome inherent limits of a Coherent Ising Machine (CIM). (The Ising model is a mathematical abstraction of magnetic systems composed of competitively interacting spins, or angular momentums of fundamental particles.)
“We are pleased with the results of our ongoing collaboration with Dr. Aonishi’s Lab at Tokyo Institute of Technology and with this research in particular, which expands the CIM’s reach to a wider array of practical applications,” said PHI Lab Director Yamamoto. “It is important that theoretical work and numerical simulation models of the CIM keep pace with the scale of experimental results; there is more to do, but the work represented in this article is a significant step in that direction.”
NTT notes that have been various attempts to harness a CIM’s optical pulses, which are mutually coupled by dissipative circuits rather than unitary gates, to solve combinatorial optimization problems, such as the traveling salesman problem, lead optimization in drug discovery, multiple-input multiple-output (MIMO) optimization for wireless communications and compressed sensing for medical imaging. In the laboratory realm, a landmark result of an experimental measurement feedback CIM with 100,000 spins was achieved in 2021. The theoretical schemes proposed in this article, by contrast, apply to modeling methodologies that simulate the behavior of a physical CIM, which allow scientists to study a CIM without needing to build one. Some of the article’s more technical findings concern the performances of those models. The primary takeaway, however, is that the proposed amplitude control scheme increases the performance for a 16-spin CIM with Zeeman terms, especially when those terms are competing against mutually coupling coefficients.
