Chiral quantum batteries

Abstract

Exploiting quantum effects for energy storage, quantum batteries (QBs) offer compelling advantages over conventional ones in terms of superior energy density, ultrafast charging, and high conversion efficiency. However, their realization is hampered by decoherence, which causes incomplete charging, rapid self-discharging, and reduced extractable work. Here, we propose a QB architecture based on a chiral magnonic platform. It comprises two yttrium iron garnet (YIG) spheres, one serving as the charger and the other as the QB, coupled to a waveguide. The unique chiral coupling between magnons and the guided electromagnetic fields breaks inversion symmetry, inducing both nonreciprocal energy flow and coherent interference between the charger and QB. Their synergy endows our QB with a 34-fold increase in energy capacity and a 55-fold boost in extractable work compared to its achiral counterpart in an experimentally accessible regime. Our scheme harnesses the decoherence from the electromagnetic fields and turns its destruction into an asset, which enables the robustness and wireless-like remote charging features of the QB. Our analysis reveals that these extraordinary capabilities stem from quantum coherence. By establishing chirality as a useful quantum resource, our work paves a viable path toward the realization of QBs.

Figures (4)

• Figure 1: Schematic of a chiral QB setup. Two YIG spheres separated by a distance $d$ are coupled to a waveguide via the chiral coupling rates $g_{L/R}$ along the $z$-axis. A static bias magnetic field $\mathcal{H}_{y}$ along the $y$-axis is applied to produce a uniform eigenfrequency of the magnons in the YIG speres. $\kappa$ is the damping rate of the magnons. The left YIG sphere acts as the charger and the right one acts as the QB.
• Figure 2: Evolution of (a) the stored energy $\mathcal{E}_\text{B}(t)$, (b) the charging efficiency $\eta(t)$ of the QB, (c) ergotropy, and (d) $R(t)$ as a function of the nonreciprocity parameter $D$ when $\Gamma_L$ varies from zero to $\Gamma_R$. The cyan solid line represents the steady-state analytical solution. The parameters are $k_0d=\pi/2$, $\omega_d=\omega_0$, $\Omega\approx0.0022\omega_0$, $\Gamma_R\approx0.001\omega_0$, $\bar{n}=0$, and $\kappa=\frac{\Gamma_R}{20}$.
• Figure 3: (a) Charging efficiency $\eta_\text{ss}$ and (b) ratio of steady-state ergotropy $\mathcal{W}_\text{ss}/\mathcal{W}_{\text{ss}|D=0}$ as a function of the nonreciprocity parameter $D$ and the QB-charger distance $d$ when $\Gamma_L$ varies from $0$ to $\Gamma_R$. The corresponding stable behavior of the quantum coherence $C_{\text{ss}|D=1}/C_{\text{ss}|D=0}$ is described by the yellow solid lines overlaid on the density plots in (b). The parameters are the same as Fig. \ref{['energy']}.
• Figure 4: (a) Chirality enhanced ratio of the steady-state QB energy $\mathcal{E}_{\text{B,ss}|D=1}/\mathcal{E}_{\text{B,ss}|D=0}$ and (b) $R_{\text{ss}|D=1}$ as a function of the QB-charger distance $d$ for different values of $\bar{n}$. Other parameters are the same as Fig. \ref{['energy']}.