China University of Science and Technology to achieve high-performance integrated solid-state quantum memory

Our school’s Guo Guangcan academician team has made important progress in the field of quantum storage. The team, Li Chuanfeng, Zhou Zongquan and others, used femtosecond laser microprocessing technology to prepare high-fidelity integrated solid-state quantum memory, and based on independent research equipment for the first time to achieve the first time the electron spin and nuclear spin coherent coherent life of a comprehensive improvement. The results were published february 20th and 28th in the prestigious physics journals Optica and Physical Review.

China University of Science and Technology to achieve high-performance integrated solid-state quantum memory

Integrated solid-state quantum storage experimental schematic

Quantum memory is the core device to construct quantum network, which can effectively overcome channel loss, thus expanding the working distance of quantum communication and can integrate quantum computing and quantum sensing resources in different places. Li Chuanfeng and Zhou Zongquan Research Group have long been committed to the study of solid-state quantum memory based on rare earth doped crystals, and the three technical indicators of solid-state quantum memory, such as fidelity, dimensional number and multi-mode capacity, have maintained international leading.

The current research of solid state quantum memory is faced with two challenges, on the one hand, the existing solid-state quantum storage experiments use most of the storage media block crystals, this material can not directly dock the optical fiber network or integrated optical chips, it is difficult to achieve large-scale scalability applications. On the other hand, the electron spin of rare earth ions and the interaction of nuclear spin with the inner soundofins of the crystal lead to severe limitation of the coherent life of quantum memory. In order to promote the practicalization of quantum memory, the research team began to carry out systematic research on the above problems from the material processing and testing equipment.

In order to solve the expansion problem, the research team used the festo-second laser micro-processing technology to etch the light waveguide in the crystal of niobium silicate for the first time, and developed an integrated solid-state quantum memory. The waveguide area is 150 microns from the crystal surface and has a waveguide width of 20 microns, which can be integrated with other microelectronics and micronano optics. Due to the high optical field power density in the waveguide area, the control laser power required for the experiment was reduced by about 30 times compared to the power required for block crystals. In the experiment, two optical quantum storage schemes, atomic frequency comb (AFC) and low noise echo recovery (ROSE), were demonstrated, and the storage fidelity was determined by the interference between the reference optical signal and the memory-readable optical signal. The corresponding fidelity of the two schemes exceeds 99% and 97% respectively, indicating that this integrated quantum memory has high reliability.

An effective solution to the problem of limited coherent life is to construct a pulsed electron and nuclear spin dual resonance spectrometer (ENDOR) at deep and low temperature (?lt;0.5K) to reduce the number of phonons and polarize electron spins. Due to the high thermal load in traditional commercial ENDOR systems, the operating temperature is generally not below 4K, and it was previously generally accepted by the international community that deep low temperature ENDOR was an unattainable task (Nature Nanotechnology 12, 958 (2017). After solving the technical problems of the series, 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 of 0.1K. At 0.1K temperature, the signal-to-noise ratio of the spin-back echo signal of the crystal edibu silicate was measured to be 20 times higher than at 4K temperature, the life and coherent life of the electron spin were 15 seconds and 2 milliseconds, respectively, while the cell-like and coherent life of the nuclear spin reached 10 minutes and 40 milliseconds, respectively, and the four life indicators achieved more than one over 4K temperature. the increase of an order of magnitude.

Optica审稿人评价:”the diversity of techniques and implemented protocols represents in overall an important amount of work which Validates FLM waveas as a hadd platform of quantum information ” (this work is very important, it demonstrates the diversity of experimental techniques and solutions, It is proved that the etched photowaveguide in rare earth doped crystals is a very promising platform in the field of quantum information.

Physical Review Applied Reviewer review: “The measurements are enabled by the development of a milliklvin adha ble of ENDOR spectroscopy, a-sb is relatively rare world wide… The sanes is likewise in, and will likely ly enable detailed spectroscopy of systems regime s it has b een hard to access before.) These measurements are based on an ENDOR spectrometer at mK-level temperature developed by the author, which is an internationalrar… This device allows some physical systems to achieve more accurate spectral analysis and enter a temperature interval that was difficult to reach. “An order of magnitude increase in both electron and nuclear spin coherence times is observed when go go 4 K to 10 0 mK. To my knowledge this is the first observation of a strong sum of spin coherence times in rare-earth doped crystals by The coherent life of electron spin and nuclear spin increases by more than an order of magnitude from 4K to 100mK. This is the first time that a significant increase in spincoherent coherent life has been observed in rare earth ions through deep and low temperatures. )”

The first authors of the two papers are Liu Chao and Li Peixuan, Ph.D. students of the Key Laboratory of Quantum Information of the Chinese Academy of Sciences. The work has been funded by the Ministry of Science and Technology, the National Natural Science Foundation of China, the Chinese Academy of Sciences and Anhui Province.

China University of Science and Technology to achieve high-performance integrated solid-state quantum memory

(a) Sample local plot (b) relationship between spin echo signal strength and operating temperature of deep cryogenic electrons and nuclear spin dual resonance spectrometers

(The Key Laboratory of Quantum Information of the Chinese Academy of Sciences, the Institute of Quantum Information and Quantum Science and Technology Innovation of the Chinese Academy of Sciences, and the Research Department)

Links to the article:

https://www.osapublishing.org/optica/abstract.cfm?uri=optica-7-2-192

https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.13.024080