Experimental optimization of charging quantum batteries through a catalyst system

Quantum batteries are quantum systems that potentially serve as fuel for other quantum devices by receiving and supplying energy. In this Letter, we investigate the charging processes of a state-of-the-art quantum battery made of a harmonic oscillator, which can store infinite amounts of energy in principle. We experimentally simulate the charging process using a high-dimensional photonic quantum system with multiple concatenated interferometers. Our experiments demonstrate that both the stored and extractable energy of the quantum battery can be significantly improved by introducing a catalyst system. This charging protocol has the same performance as optimized the frequency of the external field in the direct charging protocol but is more convenient without the requirement of probing the global frequency of the charge-battery system. From the viewpoint of experimental innovation, we propose a general method to deterministically implement an arbitrary trace-preserving nonunitary channel and realize it experimentally. Our work shows the potential of this interesting quantum battery and sheds light on experimental investigations of quantum batteries.