Collective behavior strongly influences the charging dynamics of quantum batteries (QBs). Here, we study the impact of nonlocal correlations on the energy stored in a system ofNQBs. A unitary charging protocol based on a Sachdev-Ye-Kitaev (SYK) quench Hamiltonian is thus introduced and analyzed. SYK models describe strongly interacting systems with nonlocal correlations and fast thermalization properties. Here, we demonstrate that, once charged, the average energy stored in the QB is very stable, realizing an ultraprecise charging protocol. By studying fluctuations of the average energy stored, we show that temporal fluctuations are strongly suppressed by the presence of nonlocal correlations at all time scales. A comparison with other paradigmatic examples of many-body QBs shows that this is linked to the collective dynamics of the SYK model and its high level of entanglement. We argue that such feature relies on the fast scrambling property of the SYK Hamiltonian, and on its fast thermalization properties, promoting this as an ideal model for the ultimate temporal stability of a generic QB. Finally, we show that the temporal evolution of the ergotropy, a quantity that characterizes the amount of extractable work from a QB, can be a useful probe to infer the thermalization properties of a many-body quantum system.

We consider a quantum battery that is based on a two-level system coupled with a cavity radiation by means of a two-photon interaction. Various figures of merit, such as stored energy, average charging power, energy fluctuations, and extractable work are investigated, considering, as possible initial conditions for the cavity, a Fock state, a coherent state, and a squeezed state. We show that the first state leads to better performances for the battery. However, a coherent state with the same average number of photons, even if it is affected by stronger fluctuations in the stored energy, results in quite interesting performance, in particular since it allows for almost completely extracting the stored energy as usable work at short enough times.

Describing the thermodynamic properties of quantum systems far from equilibrium is challenging, in particular when the system is strongly coupled to its environment, or when memory effects cannot be neglected. Here, we address such regimes when the system-bath couplings are periodically modulated in time. We show that the couplings modulation, usually associated with a purely dissipative effect, can be suitably engineered to perform thermodynamic tasks. In particular, asymmetric couplings to two heat baths can be used to extract heat from the cold reservoir and to realize an ideal heat rectifier, where the heat current can be blocked either in the forward or in the reverse configuration by simply tuning the frequency of the couplings modulation. Interestingly, both effects take place in the low-temperature, quantum non-Markovian regime. Our work paves the way for the use of optimal control techniques for heat engines and refrigerators working in regimes beyond standard approaches.

We consider a micromaser model of a quantum battery, where the battery is a single mode of the electromagnetic field in a cavity, charged via repeated interactions with a stream of qubits, all prepared in the same non-equilibrium state, either incoherent or coherent, with the matter–field interaction modeled by the Jaynes–Cummings model. We show that the coherent protocol is superior to the incoherent one, in that an effective pure steady state is achieved for generic values of the model parameters. Finally, we supplement the above collision model with cavity losses, described by a Lindblad master equation. We show that battery performances, in terms of stored energy, charging power, and steady-state purity, are slightly degraded up to moderated dissipation rate. Our results show that micromasers are robust and reliable quantum batteries, thus making them a promising model for experimental implementations.

In this paper we develop the theory for two-dimensional to two-dimensional tunneling spectroscopy aided by magnetic or quantum-order excitations, and apply it to the description of van der Waals heterostructures of graphene or ultrathin $\alpha -{\mathrm{RuCl}}_3$. We study the behavior of both the differential conductance and the inelastic electron tunneling spectrum (IETS) of these heterostructures. The IETS in particular exhibits features such as the gap of continuum spinon excitations and Majorana bound states, the energies of which scale cubicly with the applied magnetic field. Such scaling, which exists for a relatively wide range of fields, is at odds with the linear one exhibited by conventional magnons and can be used to prove the existence of Kitaev quantum spin liquids.

Performances of work-to-work conversion are studied for a dissipative nonlinear quantum system with two isochromatic phase-shifted drives. It is shown that for weak Ohmic damping simultaneous maximization of efficiency with finite power yield and low power fluctuations can be achieved. Optimal performances of these three quantities are accompanied by a shortfall of the tradeoff bound recently introduced for classical thermal machines. This bound can be undercut down to zero for sufficiently low temperature and weak dissipation, where the non-Markovian quantum nature dominates. Analytic results are given for linear thermodynamics. These general features can persist in the nonlinear driving regime near a maximum of the power yield and a minimum of the power fluctuations. This broadens the scope to an operation field beyond linear response.