A photonic quantum engine driven by superradiance

Performance of nano- and microscale heat engines can be improved with the help of quantum-mechanical phenomena. Recently, heat reservoirs with quantum coherence have been proposed to enhance engine performance beyond the Carnot limit even with a single reservoir. However, no physical realizations have been achieved so far. Here we report the first proof-of-principle experimental demonstration of a photonic quantum engine driven by superradiance employing a single heat reservoir composed of atoms and photonic vacuum. Reservoir atoms prepared in a quantum coherent superposition state underwent superradiance as they traversed the cavity. This led to about 40-fold increase in the effective engine temperature, resulting in near-unity engine efficiency. Moreover, the observed engine output power grew quadratically with respect to the atomic injection rate. Our work can be utilized in quantum-mechanical heat transfer as well as in boosting engine powers, opening a pathway to the development of photomechanical devices that run on quantum coherence embedded in heat baths. A superradiant photonic engine is developed by using a 138 Ba atomic beam and a high-finesse optical cavity. The mirrors of a Fabry–Pérot cavity act as the piston of an engine. The achieved engine temperature and efficiency are 1.5 × 10 5 K and 98%, respectively.