Experimental investigation of a quantum battery using star-topology NMR spin systems

Theoretical explorations have revealed that quantum batteries can exploit quantum correlations to achieve faster charging, thus promising exciting applications in future technologies. Using NMR architecture, here we experimentally investigate various aspects of quantum batteries with the help of nuclear spin systems in a star-topology configuration. We first carry out numerical analysis to study how charging a quantum battery depends on the relative purity factors of charger and battery spins. By experimentally characterizing the state of the battery spin undergoing charging, we estimate the battery energy as well as the ergotropy, the maximum amount of work that is unitarily available for extraction. The experimental results thus obtained establish the quantum advantage in charging the quantum battery. We propose using the quantum advantage, gained via quantum correlations among chargers and the battery, as a measure for estimating the size of the correlated cluster. We develop a simple iterative method to realize asymptotic charging that avoids the oscillatory behavior of charging and discharging. Finally, we introduce a load spin and realize a charger-battery-load circuit and experimentally demonstrate battery energy consumption after varying the duration of battery storage, for up to 2 min.