In collaboration with the researchers in Shanghai Jiaotong University and Oxford University, Professor Mang Feng’s group for Bound-System Quantum Information Processing at Wuhan Institute of Physics and Mathematics (WIPM), Chinese Academy of Sciences has just published their latest research results exploring thermodynamics of information in Physical Review Letters, which is selected as Editor’s Suggestion due to its importance.

 In thermodynamics, the nonequilibrium dynamic process is ubiquitous in dynamic evolutions. In general, the nonequilibrium dynamics is extremely complicated, which can be described only by inequalities. However, C. Jarzynski proposed a simple and general equality in 1997 to connect the physical quantities in the nonequilibrium process to the free-energy change of the system. This equality was further generalized by V. Vedral who proposed an new information-theoretic equality for the change of information between two different measurements during the time evolution. The new equality, which is more suitable for quantum domain, can be reduced to the Jarzynski equation when the system is initially in a Gibbs state.

Professor Feng’s group has already achieved stable confinement of ultracold ions in an electromagnetic potential well and precise manipulation of quantum states of the ions, including arbitrary quantum-state preparation, laser-controlled quantum-state time evolution, laser-phase modulation and arbitrary projection measurement. After considering the feasibility of single-qubit implementation for the information-theoretic equalities, Associate Professor Fei Zhou, Assistant Professor Leilei Yan and PhD student Taiping Xiong have designed the experimental scheme, and carried out the experiment at the level of 0.7% error of single-spin operations under the influence of quantum and classical noises. This is the first experimental verification of nonequilibrium thermodynamics of information at a single-spin level, which showed that the information-theoretic equalities, including the Jarzynski equality, work nearly perfectly at the fundamental level of a single spin. Associate Professor Wanli Yang and other members also made contributions on this work.

This work would be helpful for understanding the thermodynamic behavior at quantum mechanical level and for further exploring new physics in quantum world from the viewpoint of quantum information. The study was supported by National Key Research and Development Program of China, the Strategic Research Program of the Chinese Academy of Sciences and National Natural Science Foundation of China.

Link for the paper：https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.120.010601

Experimental measurement values of the information-theoretic equality and the total amount of information in the case of the pure states