In this work, we propose an open quantum battery that stores and releases energy by employing a two-mode ultrastrongly coupled bosonic system, with one mode (the charger) coupled to an independent heat reservoir. Our results demonstrate that both the charging energy and ergotropy of the quantum batteries can be significantly enhanced within the ultra-strong coupling regime and across a broader temperature range in transient time. A unidirectional energy flow is achieved by controlling the system's initial state through its two-mode squeezed ground state. Furthermore, we show that the steady-state stored energy, along with its corresponding ergotropy, can be enhanced at larger temperatures and stronger coupling strengths. Notably, a purely beam-splitter or two-mode squeezing interaction yields zero ergotropy. These findings indicate that the enhanced stored energy and ergotropy of the quantum battery arises principally from the combined effects of beam-splitter and parametric amplification (squeezing) couplings. In addition, the presence of the squared electromagnetic vector potential term can prevent a phase transition and achieve a significant charging energy and high ergotropy in the deep-strong coupling regime. The results presented herein enhance our understanding of the operating principles of open bosonic quantum batteries.
In this work, we propose an open quantum battery that stores and releases energy by employing a two-mode ultrastrongly coupled bosonic system, with one mode (the charger) coupled to an independent heat reservoir. Our results demonstrate that both the charging energy and ergotropy of the quantum batteries can be significantly enhanced within the ultra-strong coupling regime and across a broader temperature range in transient time. A unidirectional energy flow is achieved by controlling the system's initial state through its two-mode squeezed ground state. Furthermore, we show that the steady-state stored energy, along with its corresponding ergotropy, can be enhanced at larger temperatures and stronger coupling strengths. Notably, a purely beam-splitter or two-mode squeezing interaction yields zero ergotropy. These findings indicate that the enhanced stored energy and ergotropy of the quantum battery arises principally from the combined effects of beam-splitter and parametric amplification (squeezing) couplings. In addition, the presence of the squared electromagnetic vector potential term can prevent a phase transition and achieve a significant charging energy and high ergotropy in the deep-strong coupling regime. The results presented herein enhance our understanding of the operating principles of open bosonic quantum batteries.
Quantum batteries are quantum systems that potentially serve as fuel for other quantum devices by receiving and supplying energy. In this work, we propose a theoretical scheme to enhance ergotropy and charging power of quantum Battery in the system under consideration through squeezed light. Moreover, The system comprises a coherently driven charger cavity, a strongly dissipative auxiliary cavity acting as a mediator, and an energy--storage battery cavity. Quantum nonreciprocity and directional energy flow are established via destructive quantum interference between the direct coupling path and the loss--engineered indirect path. A degenerate optical parametric amplifier integrated into the charger cavity acts as an active, phase--sensitive energy source that injects two--photon quantum excitations and anomalous correlations. Using a strictly open--quantum--system framework derived directly from the Lindblad master equation, we obtain the full expectation--value dynamics and stationary states. We show that active parametric driving drastically increases the stored energy and peak charging power while maintaining nonreciprocal energy trapping in the battery. We achieve a multi-order-of-magnitude boost in the battery's stored energy, charging power, and ergotropy. We also analyze the effects of pure dephasing on the charging power, ergotropy, and extractable work quality.. Although two--photon pumping introduces photon--number fluctuations that slightly lower the fractional ergotropy ratio WB/EB, the absolute extractable work remains substantially elevated compared to unassisted configurations.
Quantum batteries, as highly efficient energy storage devices, have garnered significant research interest. A key challenge in their development is to maximize the extractable energy (ergotropy) when operating within a finite-temperature reservoir. To address this, we applied quantum feedback control to the charger and investigated the effects of fermionic and bosonic thermal reservoirs on the performance of quantum batteries, including stored energy, ergotropy, and charging efficiency, in an open environment. Our findings reveal that, regardless of the type of thermal reservoir, the system exhibits optimal charging parameters. In particular, in a fermionic thermal reservoir, increasing the environmental temperature enhances battery performance, enabling stable and efficient charging. In contrast, within a bosonic thermal reservoir, higher temperatures hinder energy storage and extraction, significantly reducing charging efficiency. Additionally, we explored the impact of battery size and found that, under a fermionic reservoir, increasing the battery size appropriately can further improve performance.
We explore the wireless charging of a quantum battery (QB) via n charging units, whose coupling is mediated by a common bosonic reservoir. We consider the general scenarios in which the charger energy is not maximal and the QB has residual ergotropy initially. It is found that the charging performance improves with the increase of the coupling strength. In the strong coupling regime, the charging time is insensitive to the charger energy, the number of charging units, and the residual ergotropy in the QB, while the ergotropy charged on the QB strongly depends on the charger energy and ergotropy, and the residual ergotropy in the QB does not help to enhance its performance. Moreover, the multiple charging units help to enhance the charging performance in the weak and moderate coupling regimes, while they are less efficient in the strong coupling regime.
Decoherence and dissipation in open quantum systems generally drive quantum batteries toward passive states, thereby reducing their extractable work (ergotropy). Here, we study a driven qubit quantum battery coherently coupled to an auxiliary harmonic oscillator in the presence of dephasing and dissipation. Using the differential formulation of the first law of open quantum thermodynamics, we analyze the local energy-flow dynamics during the charging process. We find that the auxiliary oscillator induces a transient negative local energy current into the qubit subsystem, corresponding to a temporary inward energy backflow. This transient energy redistribution is accompanied by an enhancement of the qubit ergotropy and a partial suppression of decoherence-induced passivation. Moreover, the parameter regime exhibiting a more pronounced negative-current interval is consistently correlated with larger ergotropy enhancement. Our results suggest that transient inward energy flow provides a useful thermodynamic signature associated with enhanced energy storage in open quantum batteries.
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.
Suppressing coherent energy backflow while maintaining extractable energy in a stable nonequilibrium state remains a central challenge for quantum energy storage. Here, we introduce a reservoir-engineered dual-charger quantum battery architecture, in which nonequilibrium dissipation is exploited as a control resource to stabilize useful stored energy. A hot-reservoir-coupled driver supplies excitations, while a cold-reservoir-coupled cache biases the resonant three-body transition toward charging and suppresses the dressed-state coherences responsible for energy backflow. This mechanism establishes a population-inverted steady state with finite ergotropy and converts reversible charger--battery exchange into persistent energy storage. For uniformly spaced multilevel batteries, we show that the stored energy and ergotropy scale approximately linearly with the number of accessible levels, while the stored-energy utilization approaches unity. The accompanying stationary heat current provides a thermodynamic signature of the charging regime. Our results demonstrate dissipation engineering as a strategy for achieving stable and scalable quantum energy storage beyond transient coherent charging protocols.