Quantum Batteries in Coherent Ising Machine

Abstract: With intensive studies of quantum thermodynamics, the quantum batteries (QBs) have been proposed to store and transfer energy via quantum effects. Despite many theoretical models, decoherence remains a severe challenge and practical platforms are still rare. Here we propose the QB based on the degenerate optical parametric oscillator (DOPO), using the signal field as the energy-storage unit. We carefully separate the ergotropy into coherent and incoherent components and find that the coherent part decays roughly half as slowly as the incoherent part. More importantly, the coherent ergotropy and the average charging power reach their respective maxima at essentially the same moment, i.e., $γ_s t \approx 10$. This coincidence defines the optimal instant to switch off the pump. Finally, coupling the QB to a two-level system (TLS) as the load, we demonstrate an efficient discharge process of the QB. Our work establishes a realistic and immediately-implementable QB architecture on a mature optical platform.