New perspectives in the theoretical study of quantum batteries

This PhD thesis addresses some of the most timely open problems in the field of quantum batteries based on realistic models of superconducting circuits. Here, both classical and quantum chargers are considered to provide effective ways to store energy inside the quantum battery. One important result is obtained studying the effects of quantum energy fluctuations on the energy storage when the charger consists of a classical external field. In this specific case it is demonstrated the advantages in using a time dependent field compared to a static one, with the possibility of achieving a full charging of the quantum battery and corresponding null fluctuations. Remarkably, this model has been implemented in the IBM quantum machine. The second original result concerns the average charging power of a Dicke quantum battery, where the charger is described by a photonic cavity, including both single-photon and two-photon interactions. Interestingly, these last processes, which were not considered before in the quantum battery literature, may lead to an improvement of the average charging power with respect to the single-photon interaction. Finally, the important issue of energy transfer processes is analyzed, both on- and off-resonance. The typical direct energy transfer is compared with the innovative cavity-mediated scenario, which allows to improve the performances of the energy transfer process off-resonance adding more and more photons inside the cavity.