Lost & Found Charge on Quantum Batteries

Francesco Campaioli, Felix A. Pollock, Sai Vinjanampathy

Sarkar, Debanjan Dey, Mondal, Mallika, Preeti Parashar +1 more

Quantum batteries are prone to losing their stored charge, when interacting with a thermal environment. However, getting a limited assistance from the thermal environment, is it possible to recover the charge back, in a reusable form? Here, we answer this question, by involving an assistance of a suitable measurement performed on the environment. This framework resembles the structure of quantum instruments in the thermodynamic scenario. Our proposed framework involves two different kind of assistance from thermal environment - one by accessing only the thermal particle, actively participating in the interaction, providing a weak retrieval of charge, while the other involves local assistance from an additional quantum system purifying the thermal environment, resulting in the strong retrieval of the lost charges. By setting the upper-bound on the amount of charges retrieved in each of these two situations, we report that their difference characterizes the amount of entanglement generated between the quantum battery and the reference system due to the thermal interaction. Finally, we exemplify the extreme instances of the difference between the weak and the strongly retrieved charges for qubit batteries.

Tanoy Kanti Konar, Jakub Zakrzewski

Nonstabilizerness plays an essential role in the efficient simulation of quantum systems on quantum computers. In this work, we investigate its role in the context of quantum batteries (QBs). To this end, we consider a system of N spin-1/2 particles, with the left half serving as the charger and the right half as the battery. By studying different classes of interactions between the charger and the battery, we quantify the amount of nonstabilizerness required to store work in the QB. Our results reveal a strong correlation between the ergotropy stored in the battery and the total nonstabilizerness of the composite system whenever the Hamiltonian preserves a U(1) symmetry. In contrast, this correspondence is generally lost for more generic interactions. A similar behavior is observed for unitary circuit dynamics. Finally, we examine the complementary scenario in which the battery is initialized in a nonstabilizer state and subsequently charged through Clifford evolution. In this case, we find that the maximum average charging power is nonmonotonic in the initial nonstabilizerness. Remarkably, the highest average power can be achieved even when the initial state carries no magic (nonstabilizerness), demonstrating that initial magic is not a necessary ingredient for generating optimal charging power.

Sagar Pokhrel, Julio R. Gea-Banacloche

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}.

Dario Ferraro, Fabio Cavaliere, Marco G. Genoni +2 more