@article {2725, title = {Energy storage and coherence in closed and open quantum batteries}, journal = {Quantum}, volume = {5}, year = {2021}, month = {7/15/2021}, pages = {505}, abstract = {

We study the role of coherence in closed and open quantum batteries. We obtain upper bounds to the work performed or energy exchanged by both closed and open quantum batteries in terms of coherence. Specifically, we show that the energy storage can be bounded by the Hilbert-Schmidt coherence of the density matrix in the spectral basis of the unitary operator that encodes the evolution of the battery. We also show that an analogous bound can be obtained in terms of the battery\&$\#$39;s Hamiltonian coherence in the basis of the unitary operator by evaluating their commutator. We apply these bounds to a 4-state quantum system and the anisotropic XY Ising model in the closed system case, and the Spin-Boson model in the open case.\ 

}, doi = {https://doi.org/10.22331/q-2021-07-15-505}, url = {https://arxiv.org/abs/2012.15026}, author = {Francesco Caravelli and Bin Yan and Luis Pedro Garc{\'\i}a-Pintos and Alioscia Hamma} } @article {2819, title = {Garc{\'\i}a-Pintos, Hamma, and del Campo Reply}, journal = {Phys. Rev. Lett.}, volume = {127}, year = {2021}, month = {7/9/2021}, pages = {028902}, abstract = {

We acknowledge that a derivation reported in Phys. Rev. Lett. 125, 040601 (2020) is incorrect as pointed out by Cusumano and Rudnicki. We respond by giving a correct proof of the claim \“fluctuations in the free energy operator upper bound the charging power of a quantum battery\” that we made in the Letter.

}, doi = {10.1103/PhysRevLett.127.028902}, author = {Luis Pedro Garc{\'\i}a-Pintos and Alioscia Hamma and Adolfo del Campo} } @article {2461, title = {Fluctuations in Extractable Work Bound the Charging Power of Quantum Batteries}, journal = {Phys. Rev. Lett. }, volume = {125}, year = {2020}, month = {7/22/2020}, abstract = {

We study the connection between the charging power of quantum batteries and the fluctuations of the stored work. We prove that in order to have a non-zero rate of change of the extractable work, the state ρW of the battery cannot be an eigenstate of a {\textquoteleft}\emph{work operator}\&$\#$39;, defined by F \≡ HW + β\−1log(ρW), where HW is the Hamiltonian of the battery and β 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 stored work 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.\ 

}, doi = {10.1103/PhysRevLett.125.040601}, url = {https://arxiv.org/abs/1909.03558}, author = {Luis Pedro Garc{\'\i}a-Pintos and Alioscia Hamma and Adolfo del Campo} } @article {2563, title = {Random Quantum Batteries}, journal = {Phys. Rev. Research }, volume = {2}, year = {2020}, month = {5/5/2020}, abstract = {

Quantum nano-devices are fundamental systems in quantum thermodynamics that have been the subject of profound interest in recent years. Among these, quantum batteries play a very important role. In this paper we lay down a theory of random quantum batteries and provide a systematic way of computing the average work and work fluctuations in such devices by investigating their typical behavior. We show that the performance of random quantum batteries exhibits typicality and depends only on the spectral properties of the time evolving operator, the initial state and the measuring Hamiltonian. At given revival times a random quantum battery features a quantum advantage over classical random batteries. Our method is particularly apt to be used both for exactly solvable models like the Jaynes-Cummings model or in perturbation theory, e.g., systems subject to harmonic perturbations. We also study the setting of quantum adiabatic random batteries.

}, doi = {https://doi.org/10.1103/PhysRevResearch.2.023095}, url = {https://arxiv.org/abs/1908.08064}, author = {Francesco Caravelli and Ghislaine Coulter-De Wit and Luis Pedro Garc{\'\i}a-Pintos and Alioscia Hamma} }