Prof. LI Chuanfeng and Prof. Zhou Zongquan 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 1950, 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.
By double rephasing the pulse in the four-level atomic system, they
manipulated the spontaneous noise emission to have a different frequency
from the signal. So it is much 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. 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.
All of these advantages bring us one closer step to long-distance quantum
communication.
Reference:
You-Zhi Ma et al, Elimination of noise in optically rephased photon echoes,
Nature Communications (2021).
DOI: 10.1038/s41467-021-24679-4
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