Enhanced charging power in nonreciprocal quantum battery by reservoir engineering

TL;DR

This work addresses the challenge of dissipative losses and backflow in quantum batteries by introducing a non-Hermitian, reservoir-engineered QB built from a charger–battery pair coupled to a strongly damped auxiliary cavity. By adiabatically eliminating the auxiliary mode, an effective NH coupling between the charger and battery is achieved, enabling directional energy transfer and high charging efficiency, including in the presence of dissipation. Key results show that under resonance the battery energy can exceed the charger energy with a steady-state ratio $E_B(∞)/E_A(∞) \approx 4 Γ^2/Λ_a^2$ and a charging efficiency $η(∞) \approx 0.78$, with the short-time power enhanced by optimal damping; operating at an exceptional point further improves robustness to parameter fluctuations. The scheme is experimentally feasible in circuit-QED and organic microcavity platforms, offering a path toward directional energy transfer and entropy management in open quantum systems.

Abstract

We propose a scheme to achieve a nonreciprocal quantum battery (QB) in the non-Hermitian (NH) system, which can overcome the intrinsic dissipation and reverse flow constraints. The design is based on a charger and a battery, which are coherently coupled and jointly interact with a bad cavity. By introducing the auxiliary bad cavity and exploiting the nonreciprocal condition, this model can harness the environmental dissipation to suppress the reverse energy transfer. Under resonant conditions, we have achieved a four ratio of the battery energy to the charger energy; in contrast, this ratio is significantly reduced under large detuning. Through damping optimization, high efficiency of the short-time charging power is attained. In comparison to the fully nonreciprocal scheme, the QB operating at the exceptional point (EP) exhibits greater resilience to parameter fluctuations. These findings highlight the potential of NH quantum engineering for advancing QB technology, particularly in regimes involving directional energy transfer, controlled dissipation, and entropy management in open quantum systems.

Figures (4)

• Figure 1: A schematic diagram of a non-Hermitian quantum battery system. The quantum charger $a$ (frequency $\omega_{a}$) interacts with the quantum battery $b$ (frequency $\omega_{b}$) with coupling strength $J$, and they collectively interact with mode $c$ with coupling strengths $g_{i}, i=a,b$, respectively. $\phi$ is the global phase between the three modes. The charger is driven by a field with amplitude $\varepsilon$ and frequency $\omega_{L}$. Here, $\kappa_{i}$ and $\gamma_{m}$ describe the damping rates of the respective modes. By projecting out mode $c$, the system will be equivalent to a direct interaction between mode $a$ and mode $b$, with a forward (backward) coupling rate $J_{+}-i\Gamma e^{i\phi}$ ($J_{-}-i\Gamma e^{-i\phi}$).
• Figure 2: (a) The time evolution of the battery energy $E_{B}$ versus detuning $\Delta$. (b) The time evolution of the charger-battery energy transfer efficiency $\eta(t)$. (c)$E_{B}(t)$ for different phases $\phi$. (d)The instantaneous charging power $P(t)$ for different $\Delta$. The relevant parameters are $\Delta_{a}^{\prime}=0$, $\varepsilon=0.1\omega$, $\phi=\pi/2$, $\Gamma_{a}=\Gamma_{b}=\Gamma=0.04\omega$, $\kappa_{a}=\kappa_{b}=0.003\omega$, $\gamma=10\omega$, and $J=\Gamma/2$.
• Figure 3: (a)The battery energy $E_{B}(t)$ and (b) $\eta(\infty)$ versus $r=\kappa_{b}/\kappa_{a}$ and the scaled time $Jt$. (c) and (d) The steady-state battery energy $E_{B}(\infty)$ and $\eta(\infty)$ for different damping ratios $r$. (e) The instantaneous charging power $P(t)$ versus $r$ and $Jt$. (f)The instantaneous charging power $P(t)$ for specific damping ratios $r=0.1$ (blue solid line), $r=1$ (red dashed line), $r=10$ (yellow dot-dashed line). Other parameters are consistent with Fig. 2.
• Figure 4: (a) The battery energy in the case of non-reciprocity ( blue solid line) and QB at EP (red dashed line) versus damping ratio $r$ for $\Delta=0$, and (b) versus $\Delta$ with $r=1$. Other parameters are consistent with Fig. 2.