Quantum-Enhanced Heat Engine Based on Superabsorption

We propose a quantum-enhanced heat engine with entanglement. The key feature of our scheme is superabsorption, which facilitates enhanced energy absorption by entangled qubits. Whereas a conventional engine with $N$ separable qubits provides power with a scaling of $P=\mathrm{\Theta }(N)$, our engine uses superabsorption to provide power with a quantum scaling of $P=\mathrm{\Theta }(N^2)$. This quantum heat engine also exhibits a scaling advantage over classical ones composed of $N$-particle Langevin systems. Our work elucidates the quantum properties allowing for the enhancement of performance.

Figure 1

Schematic of protocol for heat engine based on superabsorption. $N$ qubits interact with a cavity coupled with a thermal bath. This configuration is useful for tailoring the properties of the environment for the qubits. By repeated thermalization of the qubits and quenching of the qubit frequency, we can extract the work. A heat engine with separable states corresponds to a case with $N=1$, and we can operate $N$ separable engines in parallel.

Figure 2

Dependency of the power output $P(N)$ on the number of qubits $N$. The numerical values of the parameters are chosen as ${\omega }_A^H/2\pi =1\mathrm{GHz}$, $\mathrm{\Omega }/2\pi =31\mathrm{MHz}$, $T_H=(k_B{\beta }_H{)}^{-1}=20\mathrm{mK}$, $T_C=(k_B{\beta }_C{)}^{-1}=10\mathrm{mK}$, $g/2\pi =10\mathrm{kHz}$, $\mathrm{\Delta }\omega /2\pi =1\mathrm{MHz}$, and $\epsilon =0.001$. To change the efficiency as $\mathrm{\Delta }{\eta }_{\mathrm{E}2\mathrm{LS}}=0.2$, 0.1, and 0.05, we adjust ${\omega }_A^C$ as ${\omega }_A^C/2\pi =0.7\mathrm{GHz}$, 0.6 GHz, 0.55 GHz, and accordingly, ${\chi }_{\mathrm{conf}}$ changes as ${\chi }_{\mathrm{conf}}=399$, 248, 139, respectively [61].