In a world where the role of quantum technologies is rapidly increasing, the need for nanoscale energy storage devices is crucial. One of the promising candidates is the so-called quantum battery (QB) – a quantum system capable of storing and discharging energy. Over the past several years, there has been a great deal of theoretical work on developing practical architectures for QBs. One of the main obstacles in developing a robust QB is the leakage of stored energy from the QB to its environment. To overcome this obstacle, our group recently proposed an architecture consisting of a network of identical atoms with exchange symmetries, which supports the existence of symmetry-protected dark states – states in which the QB is decoupled from its environment [1]. It was shown that when excitation energy is stored in these states, the QB is loss-free (see Figure 1). On the other hand, when the symmetry is broken by attaching another thermal bath, for example, the QB begins to discharge its stored excitation energy (see Figure 1). These results offer a promising strategy for constructing QBs capable of operating efficiently in thermal environments.

Figure 1: Para-benzene-like network model of an excitonic QB in the storage phase (top) and discharge phase (bottom). \(T\) and \(T_p\) denote the temperatures of the thermal baths and symmetry-breaking bath, respectively.

[1] Liu, J., Segal, D., and Hanna, G. “Loss-free excitonic quantum battery.” J. Phys. Chem. C 123, 18303-18314 (2019).