China News Network, Hefei, March 8 (Reporter Wu Lan) The University of Science and Technology of China on the 8th: The academician Guo Guangcan's team at the school has made important progress in the field of quantum storage-using femtosecond laser technology to prepare high-performance integrated solid-state quantum memories .
Relevant results have been published in the well-known physics journals Optica and Physical Review Applied, respectively.
According to reports, the team Li Chuanfeng, Zhou Zongquan, etc. used femtosecond laser micromachining technology to prepare high-fidelity integrated solid-state quantum memories, and based on independent development of equipment, for the first time, the electronic spin and nuclear spin coherence life of the rare earth ions were fully improved .
Quantum memory is the core device for constructing a quantum network. It can effectively overcome the channel loss and thereby extend the working distance of quantum communication. It can also integrate quantum computing and quantum sensing resources in different places.
The current research on solid-state quantum memory faces two challenges. On the one hand, the storage media used in the existing solid-state quantum storage experiments are mostly block crystals. This kind of material cannot directly connect to optical fiber networks or integrate optical chips, which is difficult to achieve large-scale scalability. Application; on the other hand, the electron spin and nuclear spin of rare earth ions interact with phonons in the crystal, which causes the coherence life of the quantum memory to be severely limited. In order to promote the practical application of quantum memory, the research group began a systematic study of the above issues from material processing and testing equipment.
In order to solve the problem of scalability, the research group used femtosecond laser micromachining technology to etch an optical waveguide in an erbium-doped yttrium silicate crystal for the first time, and developed an integrated solid-state quantum memory. Experiments have determined that the fidelity of the two schemes exceeds 99% and 97%, respectively, indicating that this integrated quantum memory has high reliability.
Aiming at the problem of limited coherent lifetime, the international academia generally thought that deep low temperature (<0.5K) pulsed electron and nuclear spin dual resonance spectrometer is an impossible task. After solving a series of technical problems, the research team successfully built the world's first deep low temperature pulsed electron and nuclear spin dual resonance spectrometer, and strictly calibrated its minimum operating temperature to 0.1K.
At 0.1K, the measured signal-to-noise ratio of the spin echo signal of the Nd-doped yttrium silicate was 20 times higher than that at 4K, and the population life and coherence life of the electron spin reached 15 seconds and 2 respectively. At the same time, the population life and coherence life of nuclear spins reach 10 minutes and 40 ms, respectively. These four life indicators have achieved an order of magnitude improvement over 4K temperature.
Physical Review Applied reviewers evaluated that from 4K to 100mK, the coherent lifetimes of electron spins and nuclear spins have been improved by more than an order of magnitude. This is the first time that a significant enhancement of the spin coherence lifetime has been observed in rare earth ions through deep low temperature.