Experimental Analysis of Energy Transfers between a Quantum Emitter and Light Fields

Large Collective Power Enhancement in Dissipative Charging of a Quantum Battery

We consider a model for a quantum battery consisting of a collection of N two-level atoms driven by a classical field and decaying to a common reservoir. In the extensive regime, where the energy E scales as N and the fluctuations ΔE/E→0, our dissipative charging protocol yields a power proportional to N^{2}, a scaling that cannot be achieved in this regime by Hamiltonian protocols. The trade-off for this enhanced charging power is a relative inefficiency since a large fraction of the incoming energy is lost through spontaneous emission to the environment. Nevertheless, we find that the system can store a large amount of coherence and release the stored energy coherently through spontaneous emission, again with a power scaling as N^{2}.

Quantum Batteries: A Materials Science Perspective

In the context of quantum thermodynamics, quantum batteries have emerged as promising devices for energy storage and manipulation. Over the past decade, substantial progress is made in understanding the fundamental properties of quantum batteries, with several experimental implementations showing great promise. This perspective provides an overview of the solid-state materials platforms that can lead to fully operational quantum batteries. After briefly introducing the basic features of quantum batteries, organic microcavities are discussed, where superextensive charging is already demonstrated experimentally. Now, this explores other materials, including inorganic nanostructures (such as quantum wells and dots), perovskite systems, and (normal and high-temperature) superconductors. Key achievements in these areas, relevant to the experimental realization of quantum batteries, are highlighted. The challenges and future research directions are also addressed. Despite their enormous potential for energy storage devices, research into advanced materials for quantum batteries is still in its infancy. This paper aims to stimulate interdisciplinarity and convergence among different materials science research communities to accelerate the development of new materials and device architectures for quantum batteries.

Stable energy transfer of noninteracting quantum charger-battery via photonic band gap

We propose a stable charging scheme for a quantum battery in which the stable energy transfer of a noninteracting quantum charger-battery is induced by a common photonic band gap (PBG). By manipulating the transition frequency of the quantum battery to form multiple bound states, it is found that the capability of stable charging can be obtained without direct interaction between the quantum battery and the quantum charger. Among them, the formation of two bound states results in a lossless Rabi-like oscillatory behavior of the energy exchange. The formation of three bound states leads to a continuous collapse-revival process based on the oscillation of the stored energy. Particularly, the formation of three bound states also significantly enhances the energy extraction capability of the quantum battery. In addition, the stable charging scheme proposed in this paper can be further optimized from the perspective of environmental engineering. The expansion of the forbidden band gap width of the PBG environment not only enlarges the regulatory region for the formation of multiple bound states but also improves energy storage and extraction work.

Probing coherent quantum thermodynamics using a trapped ion

Quantum thermodynamics is aimed at grasping thermodynamic laws as they apply to thermal machines operating in the deep quantum regime, where coherence and entanglement are expected to matter. Despite substantial progress, however, it has remained difficult to develop thermal machines in which such quantum effects are observed to be of pivotal importance. In this work, we demonstrate the possibility to experimentally measure and benchmark a genuine quantum correction, induced by quantum friction, to the classical work fluctuation-dissipation relation. This is achieved by combining laser-induced coherent Hamiltonian rotations and energy measurements on a trapped ion. Our results demonstrate that recent developments in stochastic quantum thermodynamics can be used to benchmark and unambiguously distinguish genuine quantum coherent signatures generated along driving protocols, even in presence of experimental SPAM errors and, most importantly, beyond the regimes for which theoretical predictions are available (e.g., in slow driving).

Evaluating extractable work of quantum batteries via entropic uncertainty relations

In this study, we investigate the effectiveness of entropic uncertainty relations (EURs) in discerning the energy variation in quantum batteries (QBs) modelled by battery-charger field in the presence of bosonic and fermionic reservoirs. Our results suggest that the extractable works (exergy and ergotropy) have versatile characteristics in different scenarios, resulting in a complex relationship between tightness and extractable work. It is worth noting that the tightness of the lower bound of entropic uncertainty can be a good indicator for energy conversion efficiency in charging QBs. Furthermore, we disclose how the EUR including uncertainty and lower bound contributes to energy conversion efficiency in the QB system. It is believed that these findings will be beneficial for better understanding the role of quantum uncertainty in evaluating quantum battery performance.

Remote Charging and Degradation Suppression for the Quantum Battery

The quantum battery (QB) makes use of quantum effects to store and supply energy, which may outperform its classical counterpart. However, there are two challenges in this field. One is that the environment-induced decoherence causes the energy loss and aging of the QB, the other is that the decreasing of the charger-QB coupling strength with increasing their distance makes the charging of the QB become inefficient. Here, we propose a QB scheme to realize a remote charging via coupling the QB and the charger to a rectangular hollow metal waveguide. It is found that an ideal charging is realized as long as two bound states are formed in the energy spectrum of the total system consisting of the QB, the charger, and the electromagnetic environment in the waveguide. Using the constructive role of the decoherence, our QB is immune to the aging. Additionally, without resorting to the direct charger-QB interaction, our scheme works in a way of long-range and wireless-like charging. Effectively overcoming the two challenges, our result supplies an insightful guideline to the practical realization of the QB by reservoir engineering.