Large Collective Power Enhancement in Dissipative Charging of a Quantum Battery

We consider a model for a quantum battery consisting of a collection of N two-level atoms driven by a classical field and decaying to a common reservoir. In the extensive regime, where the energy E scales as N and the fluctuations ΔE/E→0, our dissipative charging protocol yields a power proportional to N^{2}, a scaling that cannot be achieved in this regime by Hamiltonian protocols. The trade-off for this enhanced charging power is a relative inefficiency since a large fraction of the incoming energy is lost through spontaneous emission to the environment. Nevertheless, we find that the system can store a large amount of coherence and release the stored energy coherently through spontaneous emission, again with a power scaling as N^{2}.