Abstract We study a charger-battery system consisting of two qubits coupled to a common structured reservoir, aimed at revealing how their frequency detunings from the main reservoir frequency and their coupling strengths to the reservoir affect the performance of the quantum battery (QB). It is found that an equal coupling of the qubits to the reservoir is beneficial for enhancing the charging performance. When the frequency detunings are not very large, we have the optimal extractable work and charging efficiency if the detuning of the QB is smaller than that of the charger. But when they are large, the equal detunings yield the optimal extractable work and charging efficiency, and the QB is efficiently charged independently of the system-reservoir coupling strength. Moreover, the increased charging time due to enlarged detunings can be efficiently offset by increasing the system-reservoir coupling strength.
Abstract We study a charger-battery system consisting of two qubits coupled to a common structured reservoir, aimed at revealing how their frequency detunings from the main reservoir frequency and their coupling strengths to the reservoir affect the performance of the quantum battery (QB). It is found that an equal coupling of the qubits to the reservoir is beneficial for enhancing the charging performance. When the frequency detunings are not very large, we have the optimal extractable work and charging efficiency if the detuning of the QB is smaller than that of the charger. But when they are large, the equal detunings yield the optimal extractable work and charging efficiency, and the QB is efficiently charged independently of the system-reservoir coupling strength. Moreover, the increased charging time due to enlarged detunings can be efficiently offset by increasing the system-reservoir coupling strength.
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.
We investigate the charging dynamics of a frequency-modulated quantum battery (QB) placed within a dissipative cavity environment. Our study focuses on the interaction of such a battery under both weak and strong coupling regimes, employing a model in which the quantum battery and charger are represented as frequency-modulated qubits indirectly coupled through a zero-temperature environment. It is demonstrated that both the modulation frequency and amplitude are crucial for optimizing the charging process and the ergotropy of the quantum battery. Specifically, high-amplitude, low-frequency modulation significantly enhances charging performance and work extraction in the strong coupling regime. As an intriguing result, it is deduced that modulation at very low frequencies leads to the emergence of energy storage and work extraction in the weak coupling regime. Such a result can never be achieved without modulation in the weak coupling regime. These results highlight the importance of adjusting modulation parameters to optimize the performance of quantum batteries for real-world applications in quantum technologies.
In this work, we investigate the autonomous charging process of a quantum battery coupled to a structured reservoir composed of two qubits, each locally coupled to its own bosonic thermal bath. Moreover, the reservoir interacts with a charger-battery architecture through three configurations: (I) direct coupling between reservoir qubits and battery; (II) collective coupling among the reservoir qubits, charger, and battery; and (III) a collective coupling between the reservoir qubits and charger together with a local charger-battery interaction. However, by using incoherent and coherent initial states, we analyze the stored energy, ergotropy, and charging power of the battery, and derive upper and lower bounds on the extractable work in terms of the free energy of coherence and the correlations exchanged between subsystems. Our results show that global and local coherences, as well as total correlations, act as quantum resources that enhance autonomous charging. Additionally, we demonstrate that the free energy stored in the quantum battery splits into contributions from coherence and correlations, providing numerical evidence that supports the derived ergotropy bounds. Importantly, this work highlights how structured reservoirs enable autonomous and resource-enhanced quantum battery operation.
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.
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.
Abstract Reservoir engineering has been widely used in various quantum technologies. Based on a cavity-QED (quantum electrodynamics) model, we propose a potentially practical scheme using squeezed-vacuum reservoir engineering to optimize the performance of a quantum battery (QB) located inside a cavity driven by a broadband squeezed laser, which acts as a squeezed-vacuum reservoir. Using the reduced master equation of the QB obtained via the adiabatic elimination method, we focus on the QB’s charging dynamics under tunable squeezed reservoirs governed by parametrically controlled squeezing parameters, which dictate the efficiency of energy transfer and the extractable work (ergotropy) of the QB. We show that increasing the squeezing strength improves the charging rate and enables rapid energy transfer, whereas the steady-state energy of the QB saturates at specific values of the squeezing parameter. Notably, the ergotropy of the QB reaches its maximum at a critical squeezing strength and does not scale monotonically with the squeezing strength. This nonmonotonic behavior underscores the existence of optimal parameter regimes, through which the performance of the QB can be significantly enhanced.