The photon echo protocol is a fundamental physical interaction between light and matter. It is an essential tool for the manipulation of electromagnetic fields.
Be that as it may, the extreme spontaneous noise emission generated has the same frequency as the signal; it is difficult to isolate them in principle.
Scientists from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) have raised and realized the noiseless photon echo (NLPE) protocol. Unlike previous strategies, this research reduced the noise by 670 times. Also, it achieved solid quantum memory with high fidelity.
Scientists implemented the NLPE protocol in Eu3+:Y2SiO5 crystal to serve as an optical quantum memory. It also applied a four-level atomic system to suppress the noise.
By double rephasing the pulse in the four-level atomic system, they controlled the spontaneous noise emission to alternate frequencies from the signal. This made it a lot simpler to separate the signal from the noise emission. However, different noises were recognized in experiments, and they were estimated to be trivial.
The results show that the noise was 0.0015 photons, 670 times less than previous results. Besides, the efficiency of NLPE was more than three times larger than that of previous protocols.
Furthermore, its high efficiency, high fidelity, and easy-to-achieve entitle NLPE with magnificent benefits as a noiseless quantum memory protocol.
- Ma, YZ., Jin, M., Chen, DL. et al. Elimination of noise in optically rephased photon echoes. Nat Commun 12, 4378 (2021). DOI: 10.1038/s41467-021-24679-4