Ergotropy serves as a key indicator for assessing the performance of quantum batteries (QBs). Using the Redfield master equation, we investigate ergotropy dynamics in a non-Markovian QB composed of an N-spin chain embedded in a microcavity. Distinct from the Markovian charging process, the thermal charging process exhibits a distinct oscillatory behavior in the extracted ergotropy. We show that these oscillations can be effectively suppressed through coordinated tuning of coherent driving, cavity parameters, and spin-spin couplings. In addition, we analyze the influence of various system and environmental parameters on the time evolution of ergotropy, revealing rich dynamical features. Our results offer insights into the control of energy extraction in QBs and may inform future designs of practical battery architectures.
Ergotropy serves as a key indicator for assessing the performance of quantum batteries (QBs). Using the Redfield master equation, we investigate ergotropy dynamics in a non-Markovian QB composed of an N-spin chain embedded in a microcavity. Distinct from the Markovian charging process, the thermal charging process exhibits a distinct oscillatory behavior in the extracted ergotropy. We show that these oscillations can be effectively suppressed through coordinated tuning of coherent driving, cavity parameters, and spin-spin couplings. In addition, we analyze the influence of various system and environmental parameters on the time evolution of ergotropy, revealing rich dynamical features. Our results offer insights into the control of energy extraction in QBs and may inform future designs of practical battery architectures.
The performance of open quantum batteries (QBs) is severely limited by decoherence due to the interaction with the surrounding environment. So, protecting the charging processes against decoherence is of great importance for realizing QBs. In this work we address this issue by developing a charging process of a qubit-based open QB composed of a qubit-battery and a qubit-charger, where each qubit moves inside an independent cavity reservoir. Our results show that, in both the Markovian and non-Markovian dynamics, the charging characteristics, including the charging energy, efficiency and ergotropy, regularly increase with increasing the speed of charger and battery qubits. Interestingly, when the charger and battery move with higher velocities, the initial energy of the charger is completely transferred to the battery in the Markovian dynamics. In this situation, it is possible to extract the total stored energy as work for a long time. Our findings show that open moving-qubit systems are robust and reliable QBs, thus making them a promising candidate for experimental implementations.
Ergotropy--a key figure of merit for quantum battery (QB) performance--plays a crucial role. However, the dynamics and physical mechanisms governing ergotropy evolution remain open challenges. Here, we investigate the ergotropy of a general QB model and find that the charging process is accompanied by the variation and inversion of the energy level populations. In the absence of population inversion, the ergotropy is fully consistent with coherent ergotropy; in local and global population inversion, it is determined by both coherent and incoherent ergotropy. Via random sampling of quantum states and Hamiltonians, we show that coherence and the participation ratio enhance coherent ergotropy, whereas incoherent ergotropy--whether enhanced, unchanged, or suppressed--depends on diagonal entropy, the participation ratio, and energy level population ordering. We demonstrate that the ergotropy lower bound is incoherent ergotropy, the upper bound is the QB stored energy, and enhanced QB purity suppresses locked energy and boosts charging efficiency. Furthermore, we use the Tavis-Cummings (TC) and Jaynes-Cummings (JC) batteries as paradigms to validate our findings. Our work elucidates ergotropy underlying mechanisms in general QBs and establishes a rigorous framework for optimizing ergotropy and charging efficiency, paving the way for high-performance quantum energy-storage devices.
Quantum batteries (QBs) have emerged as a promising route for fast energy storage and on-chip power supply in quantum devices. Given the limited analytical understanding of open Floquet QBs, we employ the kicked-Ising model as a tractable platform to systematically study its performance under realistic conditions, including finite temperature effects and environmental dissipation. Starting from Gibbs states of the transverse-field Ising model, we incorporate thermal and decoherence effects along the evolution, using both analytical and numerical approaches. Taking ergotropy as a central figure of merit, we characterize the injected and extractable energy, and identify regimes where charging remains robust despite environmental effects. Our results provide a systematic framework for assessing QB performance under thermal and dissipative effects.
A quantum battery is a temporary energy-storage system. We construct a quantum battery model of an N-spin chain with nearest-neighbor hopping interaction and investigate the quantum battery's charging process. We obtain the maximum energy in the quantum battery charged by a coherent cavity driving field or a thermal heat bath. We confirm that for a finite-length spin chain, thermal charging results in a nonzero ergotropy, contradicting a previous result: An incoherent heat source cannot charge a single-spin quantum battery. The nearest-neighbor hopping interaction induces energy-band splitting, enhancing the energy storage and the ergotropy of the quantum battery. We find a critical point in the energy and ergotropy resulting from the ground-state quantum phase transition after which the energy significantly enhances. Finally, we also find that disorder increases the energy of the quantum battery.
We revisit the adiabatic charging of a three-level QBs, using the adiabatic quantum master equation formalism. We restrict ourselves to the weak-coupling regime with an Ohmic thermal bath and investigate the effects of relaxation and dephasing on the charging process. We analyze the dependence of the stored energy, ergotropy as well as efficiency of QB on the total time of evolution tf. We demonstrate that for very short charging time (tf), where the evolution is highly non-adiabatic, the stored energy and ergotropy are very small. However, with increasing tf we show that there is an optimal charging time, tfopt, for maximum energy charging such that at low temperatures we could fully charge the battery and effectively extract the whole amount of energy from it. Note that, the optimal charging time could be decreased by adjusting strength of the coupling between system and environment and also appropriate choice of the Hamiltonian parameters which in turn speed up the charging process. On the other hand, we show that for very long charing time tf the charging energy, ergotropy and efficiency decrease due to thermal excitations. Furthermore to get more insights about the problem we investigate the distance between density matrix of system at optimal charging time tfopt and the corresponding thermal state using one-norm distance.
In the field of quantum thermodynamics, optimizing the performance of quantum battery (QB) under environmental effects remains a primary research interest. However, environmental control remains challenging due to its high-dimensional degrees of freedom, particularly in the non-Markovian regimes. This work investigates the charging dynamics of a QB model subjected to a tunable non-Markovian environment. We show that a controllable non-Markovian setting can be exploited to improve the QB's primary figure of merit. Specifically, we show that by tuning the relative ratio of QB-charger coupling strength and charger-bath coupling strength, the maximum dynamic values of the charging power, energy storage, and work extraction of QB can be significantly increased. Our findings suggest that employing non-Markovian effects in a tunable way offers a promising avenue for enhancing the performance of quantum thermodynamic devices, and sheds new light on the intersection between the reservior engneering and quantum thermodynamics.