Observing a Phase Transition in a Coherent Ising Machine
Hiroki Takesue, Yasuhiro Yamada, Kensuke Inaba, Takuya Ikuta, Yuya Yonezu, Takahiro Inagaki, Toshimori Honjo, Takushi Kazama, Koji Enbutsu, Takeshi Umeki, Ryoichi Kasahara · Physical Review Applied · 2023
Here researchers investigate how well a coherent Ising machine (CIM), based on a network of degenerate optical parametric oscillators, simulates the thermodynamic properties of a two-dimensional square-lattice Ising model. Assuming that the CIM samples can be regarded as a canonical ensemble, the authors estimate the effective temperature of spins (optical pulses) using maximum-likelihood estimation. Using that temperature, the thermodynamic quantities obtained from the CIM exhibit phase-transition-like behavior that matches analytical and numerical results better than what the mean-field approximation produces. This result shows the promise of physical thermodynamics simulators.