We study the connection between the charging power of quantum batteries and the fluctuations of the extractable work. We prove that in order to have a nonzero rate of change of the extractable work, the state ${\rho }_{\mathcal{W}}$ of the battery cannot be an eigenstate of a “free energy operator,” defined by $\mathcal{F}\equiv H_{\mathcal{W}}+{\beta }^{-1}\log ({\rho }_{\mathcal{W}})$, where $H_{\mathcal{W}}$ is the Hamiltonian of the battery and $\beta$ is the inverse temperature of a reference thermal bath with respect to which the extractable work is calculated. We do so by proving that fluctuations in the free energy operator upper bound the charging power of a quantum battery. Our findings also suggest that quantum coherence in the battery enhances the charging process, which we illustrate on a toy model of a heat engine.

Close

PrevNext

View figure in article

• Quantum correlations, foundations & formalism
• Quantum thermodynamics
• Quantum heat engines & refrigerators