Phys.org  August 16, 2021
The intense spontaneous noise emission generated by photon echo is a fundamental tool for the manipulation of electromagnetic fields. However, it has the same frequency as the signal, and it is impossible to separate them in principle. Researchers in China have implemented a noiseless photon echo (NLPE) protocol in Eu3+:Y2SiO5 crystal to serve as an optical quantum memory and applied a four-level atomic system to suppress the noise. They manipulated the spontaneous noise emission to have a different frequency from the signal making it easier to separate the signal from the noise emission. Though other noises were detected in practical experiment, they were all estimated to be trivial. The results of the experiments showed that the noise was 0.0015 photons, 670 times less than previous results and the efficiency of NLPE was more than three times larger than that of previous protocols, according to the researchers…read more. Open Access TECHNICAL ARTICLEÂ
Energy level diagram and experimental sequence. Credit: Nature Communications volume 12, Article number: 4378 (2021)Â