Prof. Chuanfeng Li and Prof. Zongquan Zhou from University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) innovatively raised and realized noiseless photon echo (NLPE) protocol. The research of entire originality reduced the noise by 670 times compared with previous strategies and achieved solid quantum memory with high fidelity. The results were published in Nature Communications.

First observed by Erwin Hahn in 1,950 photon echo is a fundamental physical interaction between light and matter as well as an essential tool for the manipulation of electromagnetic fields. However, the intense spontaneous noise emission generated has the same frequency as the signal, it is impossible to separate them in principle. Previous protocols, such as atomic frequency comb and the revival of silenced echo, failed to eliminate the spontaneous noise emission as much as needed.

In this study, the researchers implemented NLPE protocol in Eu3+:Y2SiO5 crystal to serve as an optical quantum memory and applied a four-level aromic system to suppress the noise.