Coherent Potts machine based on an optical loop with a multilevel phase-sensitive amplifier

Abstract

The Potts model is an extended version of the Ising model that has been intensively studied for applications in physical computers solving combinatorial optimization problems. This study proposes a coherent Potts machine (CPM), named after the coherent Ising machine (CIM), which is a type of Ising-model-based physical computer. A phase-sensitive amplifier (PSA) used in a CIM based on an optical loop with a measurement feedback system is replaced with a multilevel PSA, owing to which the optical pulses in the loop behave as Potts spins of multivalued discrete states. The operation of the proposed CPM was analyzed and numerically simulated using a traveling-wave model, demonstrating its capability to solve a graph coloring problem.