Precision Measurement Institute And Others Make Progress in Experimental Exploration Of Quantum Engines

The Bound System Quantum Information Processing Research Group of the Institute of Precision Measurement Science and Technological Innovation of the Chinese Academy of Sciences (IPMSI), in collaboration with the Guangzhou Industrial Technology Research Institute (GITRI) and others, has experimentally explored the effect of entanglement as a quantum resource on a quantum engine based on the Ultracold 40Ca+ Ion Experimental Platform. The experimental results show that the quantum engine can output more useful work when its working matter is in the entangled state, indicating that entanglement can be used as a "fuel".
Entanglement is a unique quantum resource in information processing, which can speed up computation, ensure information security in communication, and improve the accuracy of measurement. Currently, it is not entirely clear whether entanglement can play a role in energy conversion and use; whether quantum engines with entanglement properties are superior to classical engines and under what conditions this occurs is inconclusive. At the same time, there are few experimental studies of quantum engines with quantum entangled systems as the working matter, and there is no quantitative experimental verification.
The group designed a quantum engine with entanglement properties using ultracold 40Ca+ ions stably bound in an ion trap as the working material. The quantum engine carries a quantum load. It is filled by a quantum vibrational mode shared by the ions. The researchers used a thermodynamic cycle to make the quantum engine convert the photon energy of the laser through the working substance (the ion) into the phonon energy of the quantum load, and defined the conversion efficiency. Further, to estimate how much of this converted energy is extractable energy i.e. useful work, the researchers defined the mechanical efficiency.
To verify the role of entanglement in quantum engines, the study quantitatively assessed the performance of quantum engines by adjusting the entanglement of the working matter. In the experiment, the study controlled the timing of the entanglement logic gate operation by precisely manipulating the laser to obtain working matter with different degrees of entanglement. Meanwhile, the study obtained the conversion efficiency and mechanical efficiency at different entanglement degrees by measuring the number of photons absorbed in the working matter and the number of phonons added in the load. The experiments show that the maximum value of the mechanical efficiency occurs at the point where the working matter is maximally entangled, but the conversion efficiency is almost unaffected by the degree of entanglement. Analysis of the experimental data shows that the quantum engine is able to output more useful work when its working matter is in the entangled state; and the conversion efficiency of the quantum engine is independent of the entanglement, as well as the output of useful work.
This result provides experimental evidence that entanglement can play the role of "fuel" in quantum engines, and suggests that the research and development of quantum engines should pay more attention to mechanical efficiency rather than conversion efficiency. These results provide a new perspective for the development of microscopic energy devices such as quantum motors and quantum batteries.