We propose and investigate the performance of a hybrid quantum battery, the so-called Kerr quantum battery, which consists of two interacting quantum oscillators, i.e., the charger is a harmonic oscillator and the battery is an anharmonic oscillator involving the Kerr nonlinearity. Such a setup creates nonuniform spacing between energy levels of the quantum oscillator that increases with the energy level. We find that the Kerr quantum battery can store more energy than the qubit battery and reaches maximum stored energy faster than the harmonic oscillator battery. In particular, the average charging power of the Kerr quantum battery is larger than the qubit battery. Furthermore, most of the stored energy in the Kerr quantum battery can be extracted for work. All of the properties of the Kerr quantum battery are controlled by the strength of nonlinearity, in which the enhancement of the nonlinearity transforms the battery from a harmonic oscillator to a qubit.
We propose and investigate the performance of a hybrid quantum battery, the so-called Kerr quantum battery, which consists of two interacting quantum oscillators, i.e., the charger is a harmonic oscillator and the battery is an anharmonic oscillator involving the Kerr nonlinearity. Such a setup creates nonuniform spacing between energy levels of the quantum oscillator that increases with the energy level. We find that the Kerr quantum battery can store more energy than the qubit battery and reaches maximum stored energy faster than the harmonic oscillator battery. In particular, the average charging power of the Kerr quantum battery is larger than the qubit battery. Furthermore, most of the stored energy in the Kerr quantum battery can be extracted for work. All of the properties of the Kerr quantum battery are controlled by the strength of nonlinearity, in which the enhancement of the nonlinearity transforms the battery from a harmonic oscillator to a qubit.
We analyze the performance of a quantum battery in terms of energy storage and energy extraction, assisted by nonlinearities in a charger-battery system utilizing an open-system approach. In particular, we consider two types of nonlinearities in the system, viz. nonlinearity in the coupling between battery and charger, and the charger itself comprising an anharmonic oscillator. In both these scenarios, the charger is connected to an environment, and is driven by an external laser source. We derive the Markovian master equation for the dynamics of the combined charger-battery system in presence of the environment. When the charger is non-linearly coupled to a battery, we find an enhancement in the steady state ergotropy over the linearly-coupled case. We further see that the times at which steady state and maximum ergotopies are attained get decreased in presence of non-linear coupling. We also identify instances where no ergotropy is obtained in the linear case, but can be obtained in presence of any non-zero value of nonlinearity. We additionally find a complementarity between the non-linear interaction strength and the coherent-drive strength in the steady-state ergotropy values, i.e. the same ergotropy as that obtained using weak nonlinearity and strong coherent drive can be obtained utilizing an opposite order of their values. In case when the charger is modeled as a multi-level transmon with an inherent anharmonicity, we find an advantage in maximum ergotropy values over the harmonic instance. Unlike the non-linearly coupled batteries, the ones mediated by an anharmonic charger prove to be useful in the transient regime. We also determine values of the coherent drive for which the anharmonic battery is beneficial over the harmonic one at all timescales. Further, we observe a distinct region of the anharmonic strength and coherent drive where ergotropy values reach their maxima.
A quantum battery consisting of two coupled qubits driven by a delta-pulse is investigated. By using the framework of open quantum system, we obtain analytically several quantities describing the performance of the quantum battery. In particular, we are interested in the stored energy and the extractable energy known as ergotropy. We discover that by tuning the driving strength and the coupling strength, we can isolate the origin of the ergotropy: quantum coherences, population inversion, or combination of them. Furthermore, increasing the coupling strength not only enhances the stored energy, the ergotropy and charging power, but also reducing the charging time, which boosts the performance of the quantum battery.
Abstract We investigate the charging of a nonlinear quantum battery consisting of a single bosonic mode subject to a saturable nonlinearity, coherent driving, and dissipation. In contrast to Kerr-type anharmonicities, the saturable interaction induces a bounded and nonlinear distortion of the energy spectrum, leading to a progressive increase in the density of energy levels. We analyze the time evolution of the energy and ergotropy of the battery by solving a Lindblad master equation and show that the nonlinear spectral structure significantly affects both transient charging behavior and steady-state properties. Our results reveal that, for a broad range of parameters, the saturable nonlinearity enhances the maximum stored energy and modifies the ergotropy generation in the presence of losses. The interplay between dissipation and bounded spectral nonlinearity provides a controllable mechanism to tune energy storage and work extraction in bosonic quantum batteries.
We propose a design of a quantum battery exploiting the non-Hermitian Hamiltonian as a charger. In particular, starting with the ground or the thermal state of the interacting (noninteracting) Hamiltonian as the battery, the charging of the battery is performed via parity-time (PT)- and rotational-time (RT)-symmetric Hamiltonians to store energy. We report that such a quenching with a non-Hermitian Hamiltonian leads to an enhanced power output compared to a battery with a Hermitian charger. We identify the region in the parameter space which provides the gain in performance. We also demonstrate that the improvements persist with the increase of system size for batteries with both PT- and RT-symmetric chargers. In the PT-symmetric case, although the anisotropy of the XY model does not help in the performance, we show that the XXZ model as a battery with a non-Hermitian charger performs better than that of the XX model having certain interaction strengths. We also exhibit that the advantage of non-Hermiticity remains valid even at finite temperatures in the initial states.
Abstract Quantum control allows us to address the problem of engineering quantum dynamics for special purposes. While recently the field of quantum batteries has attracted much attention, optimization of their charging has not benefited from the quantum control methods. Here we fill this gap by using an optimization method. We apply for the first time the convergent iterative method for the control of the population of a bipartite quantum system in two cases, starting with a qubit-qubit case. The quantum charger-battery system is considered here, where the energy is pumped into the charger by an external classical electromagnetic field. Secondly, we systematically extend our investigation to a second case involving two harmonic oscillators in the Gaussian regime, presenting an original formulation of the method. In both cases, the charger is considered to be an open dissipative system, as its interaction with the drive may require a more pronounced exposure to general interaction with environment. A key consideration in our optimization strategy is the practical concern of turning the charging external field on and off. We find that optimizing the pulse shape yields a substantial enhancement in both the power and efficiency of the charging process compared to a sinusoidal drive. The harmonic oscillator configuration of quantum batteries is particularly intriguing, as the optimal driving pulse remains effective regardless of the environmental temperature. This study introduces a novel approach to quantum battery charging optimization, opening avenues for enhanced performance in real-world applications.
We investigate the charging of a nonlinear quantum battery consisting of a single bosonic mode subject to a saturable nonlinearity, coherent driving, and dissipation. In contrast to Kerr-type anharmonicities, the saturable interaction induces a bounded and nonlinear distortion of the energy spectrum, leading to a progressive increase in the density of energy levels. We analyze the time evolution of the energy and ergotropy of the battery by solving a Lindblad master equation and show that the nonlinear spectral structure significantly affects both transient charging behavior and steady-state properties. Our results reveal that, for a broad range of parameters, the saturable nonlinearity enhances the maximum stored energy and modifies the ergotropy generation in the presence of losses. The interplay between dissipation and bounded spectral nonlinearity provides a controllable mechanism to tune energy storage and work extraction in bosonic quantum batteries.