Efficient wireless charging of a quantum battery (2501.08843v2)

Abstract: 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.

• The paper demonstrates that optimizing the coupling strength between charging units and a bosonic reservoir significantly enhances the ergotropy of a quantum battery.
• The study reveals that initial conditions, such as sub-maximal charger energy or residual ergotropy, play a crucial role in the charging efficiency.
• The paper finds that while quantum correlations can boost charging performance under certain parameters, using multiple qubit chargers does not always yield proportional gains.

Efficient Wireless Charging of a Quantum Battery

The paper "Efficient Wireless Charging of a Quantum Battery" by Ming-Liang Hu, Ting Gao, and Heng Fan explores the intricacies of charging quantum batteries (QBs) using wireless methods facilitated by a bosonic reservoir. This research explores the dynamics of transferring energy from multiple charging units to a QB in scenarios where traditional constraints, such as maximal charger energy or fully discharged QBs, are not imposed. The findings of this paper broaden the comprehension of quantum thermodynamics and propose innovative strategies to optimize the performance of QBs in practical applications.

Overview of the Research

The researchers investigate the charging mechanism of a QB via $n$ qubit charging units in a structured bosonic reservoir. They address two pivotal scenarios:

1. Scenario I: The charging units are not fully excited, hence the charger energy is sub-maximal, while the QB is initially in a passive state, meaning it is fully discharged but not necessarily in the ground state.
2. Scenario II: The charging units are in a fully excited state, and the QB contains residual ergotropy, meaning some extractable work is initially available.

The authors underscore the coupling strength between the charging units and the reservoir as a crucial factor influencing the efficiency of energy transfer and the resultant ergotropy of the QB. The ergotropy, defined as the maximal extractable work from a QB, serves as a primary metric for assessing charging performance.

Numerical Results and Findings

The paper presents several notable outcomes:

• Coupling Strength Impact: The charging efficiency significantly improves with increased coupling strength between the qubits and the reservoir. In the strong coupling regime, the QB can be charged rapidly and efficiently, nearly reaching theoretical limits where the charger energy is almost entirely converted into ergotropy.
• Initial Conditions: The ergotropy drawn from the QB in Scenario II often mirrors the initial residual ergotropy in weaker coupling regimes, indicating that an optimal charging condition may require starting from a fully discharged state.
• Multiple Chargers: Interestingly, utilizing multiple charging units ($n \ge 2$) does not proportionally increase ergotropy performance in strong coupling regimes. However, in weak coupling environments, they can provide an advantage, especially when initial charging energy is insufficient.
• Charger State Correlations: The paper explores the role of quantum correlations in the initial charger state. While entangled states like $|\Psi^{+}\rangle$ can, under certain conditions, enhance the charging efficiency compared to product states, this effect is not universally superior and depends on specific parameter regions.

Implications and Future Directions

The findings of this paper suggest several practical and theoretical implications:

• Enhanced Wireless Charging Design: The work indicates that optimizing coupling parameters is key to achieving efficient wireless charging of QBs, guiding experimental designs for practical quantum battery implementations.
• Quantum Advantage Strategy: Identifying scenarios where quantum correlations in charging units can be harnessed for improved performance may inspire new methodologies for energy management in quantum technologies.
• Broader Applications and Model Extensions: The paper sets the groundwork for extending this theoretical analysis to other types of structured reservoirs, different spectral densities, and varying qubit-cavity detunings, potentially adding layers of understanding to environmental interactions in quantum systems.

In conclusion, this research adds depth to the field of quantum battery technology, illustrating complexities in wireless charging mechanisms that account for initial energy conditions and coupling dynamics. This work should inform future efforts to develop advanced quantum devices with practical application in quantum computing and energy storage systems.