Chinese University of Science and Technology successfully developed solid-state quantum memory with multiple degrees of freedom parallel multiplexing

The reporter learned from the University of Science and Technology of China that the academician Guo Guangcan's team Li Chuanfeng, Zhou Zongquan and others successfully developed a multi-degree-of-freedom parallel multiplexed solid-state quantum memory. And any photon pulse operation function with frequency freedom. The result was recently published in the international journal Nature.

Due to the insurmountable fiber channel loss, the current ground safety quantum communication distance is limited to the order of one hundred kilometers. The quantum relay scheme based on quantum memory can effectively overcome the channel loss and expand the working distance of quantum communication, so quantum memory is the core device of future long-range quantum communication and quantum networks. For quantum memory, due to quantum coherence, one storage unit can store a large number of qubits at once, which is the concept of multiplexing. In principle, all degrees of freedom of quantum memory can be multiplexed.

In order to further improve the multiplexing capacity of quantum memory, the research group innovatively adopted a multiple-freedom parallel multiplexing storage scheme. For example, there are M storage modes in the first degree of freedom, N modes in the second degree of freedom, and P modes in the third degree of freedom, then the total multiplexing mode number of quantum memory is the product of the number of modes , Ie M × N × P. The research team selected the photon time, space and frequency degrees of freedom for multiplexing in parallel, and was the first in the world to realize multiplexing quantum storage with these three degrees of freedom. In the experiment, 2 time modes, 2 frequency modes, and 3 spatial modes were used, and the total number of modes reached 2 × 2 × 3 = 12. The experimental results showed the feasibility of multiple-freedom parallel multiplexing quantum storage.

The research team further proved that their memory can implement arbitrary pulse operations in time and frequency degrees of freedom. Representative operations include pulse sequencing, beam splitting, frequency division, inter-frequency photon combining, and narrow-band filtering. The experimental results show that during all these operations, the three-dimensional quantum states carried by the photon maintain a fidelity of about 89%. This achievement is also expected to achieve more applications in linear optical quantum computing and other fields. (Reporter Wu Changfeng)

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