Closed-loop three-level charged quantum battery

Quantum batteries are energy storage or extraction devices in a quantum system. Here, we present a closed-loop quantum battery by utilizing a circularly coupled three-state quantum system, and investigate its charging dynamics. The charging performance is greatly improved due to the existence of the third field in the system to form a closed-contour interaction. Through appropriately selecting the third control field, the maximum average power can be increased, even far beyond the ideal maximum power value of non-closed-loop three-level quantum battery. We study the effect of the global driving-field phase on the charging process and find that both the maximum extractable work (ergotropy) and the charging power vary periodically under different control fields, with a period of . Possible experimental implementation in nitrogen-vacancy spin is discussed as well.