For the first time in the world: China to achieve 100 millisecond-level efficient quantum memory

China University of Science and Technology Pan Jianwei, Bao Xiaohui and other cold atomic ensemble in the world for the first time to achieve a hundred millisecond high-efficiency quantum memory for long-distance quantum relay system builds a solid foundation. The results published on May 31 in the international authoritative academic journal "Nature · Photonics" on. Reviewers are highly recognized for the importance of this work and praised the experiment as an extraordinary tour de force.

According to observer network reports, quantum relays can solve the major problem of exponential decay of photonic signals in optical fiber and are one of the important ways to realize ultra-long-distance quantum communications in the future. Quantum communication is considered as an absolutely secure means of communication, the basic principle of which is to use a single photon to encrypt information carrying one qubit for transmission. At present, quantum communication can only reach the level of hundreds of kilometers. To achieve long-range quantum communication over a thousand kilometers, quantum-based quantum relay technology is needed.

Quantum relay scheme has been achieved before, long-distance transmission of a quantum bit of information required time in minutes or more. The basic principle of quantum relay is to expand the communication distance by using the split-entanglement distribution and entanglement exchange. The core of the quantum relay is the quantum storage technology, which can significantly improve the efficiency of entanglement connection by buffering the photon bits. To meet the actual needs of long-distance quantum relays, quantum memories need long-term storage of single-quantum states and high readout efficiency.

In recent years, experimental research on quantum memory has been progressing rapidly. However, no system has so far fulfilled the requirements of quantum relaying in terms of storage time and efficiency. Cold atomic ensemble is an important physical system for quantum storage experimental research. Its main advantages include rich manipulation means and simple decoherence mechanism.

In order to further improve the storage time, Pan Jianwei team developed a number of key experimental techniques such as limiting the atomic motion of the three-dimensional optical lattice in recent years, which greatly suppressed the decoherence caused by atomic motion and finally achieved a storage life of 0.22 seconds. 76% efficient high-performance quantum memory. Compared with the work in 2012, this experimental result shows that the storage life is increased by nearly two orders of magnitude.

The significance of this experiment lies in, for the first time, improving the storage life and read efficiency to meet the actual needs of long-distance quantum relays. It is estimated that the combination of multimode storage and efficient communication interfaces, etc., has been able to support the entanglement distribution of more than 500 km through quantum relay and beyond the direct optical fiber transmission limit.

The research work has been supported by the Chinese Academy of Sciences Center for Quantum Information and Quantum Technology excellence innovation, Chinese Academy of Sciences - Alibaba Quantum Computing Laboratory, Fund Commission, Ministry of Science and Technology, the Mainland Ministry of Education and other relevant state departments.

Related research progress

In 2012, for the first time, Pan Jianwei and Bao Xiaohui realized millisecond efficient quantum memory, but the storage time is still far away from the actual needs of long-distance quantum relays.

In May 2012, Li Chuanfeng, a key member of the CAS Key Laboratory of Quantum Information and Information Science under the leadership of Guo Guangcan, a member of the Chinese Academy of Sciences, was the first in a solid-state system to achieve single-photon polarization quantum memories with a fidelity of 99.9% and set a world record.

In 2013, the world's first quantum memory capable of storing single-photon shapes was born in mainland China.

In August 2015, Li Chuanfeng's research group successfully developed high-dimensional solid-state quantum memories for the first time.

In October 2015, Li Chuan-feng's research group succeeded in achieving deterministic single-photon multi-mode solid-state quantum storage that can store up to 100 qubits at a time, creating the highest level in the world.