Fault-tolerant quantum computation: Attraction of all-optical control


Credit: ©Science China Press

Modern IT is based on the IC of semi-conductors. However, as the size a transistor is so small that the quantum effect of a IC is no longer negligible. Therefore, explore quantum devices that can operate single quantum particle is one of the possible ways out of the bottle-neck of Moore's law. There are many potential applications of quantum computation in various fields, such as Information security, Weather forecasting, gene sequencing, chemical synthesis and drug development, big data analysis, prediction and risk modeling, artificial intelligence, etc.

Geometric phases may also be accumulated in a quantum evolution besides the conventional dynamical phases. However, unlike the dynamical phases, geometric phases are only depends on the global properties of the quantum evolution, i.e., do not depends on the evolution details. Therefore, quantum gate induced by geometric phases will immune to operational imperfection and noises. As quantum systems are very fragile to external noises, holonomic quantum computation, where quantum gates are constructed by non-Abelian geometric phases, is one of the most promising ways for quantum computation. Meanwhile, due to its fast nature, nonadiabatic operations can be used to realize quantum gates with shorter time, and thus leads to high fidelity. Up to now, the most efficient way for nonadiabatic holonomic quantum computation is based on laser driving three level quantum systems.

Recently, a research work, published in Sci. China-Phys. Mech. Astron. 61, 010312 (2018), provides a fast scheme for holonomic quantum computation based on Nitrogen-vacancy center electron spins in diamond with all-optical control, which is led by Prof. Zheng-Yuan Xue form South China Normal University and Associate Professor Jian Zhou from Anhui Xinhua University.

Nitrogen-vacancy center electron spins in diamond possess long coherent times even at room-temperature and can be conveniently manipulated by both microwave and optical fields. In recent years, holonomic quantum operation for a single electron spin is achieved with both microwave and optical control. However, due to the complicated technique required, two spins joint operation, which is harder and essential for quantum computation, is not reported by optical control.

This research implements both the single and two-spin joint operations with all optical control, and thus presents a promising way towards robust quantum computation in this solid-state quantum system.

"We design a simplified Hamiltonian for the two-spin operations. Fortunately, it also demands very simple implementation when deal with the cavity-assisted laser diving system", explained by Dr. Jian Zhou. "Furthermore, the optical control over the quantum system is also compatible to the initialization and read-out of the system, and thus makes our proposal an experimental-friendly one."

"Due to the limited size of the cavity, only a small number of NV centers can be attached. To propose a scalable scheme, a coupled cavity scenario can be used.", explained by Prof. Zheng-Yuan Xue.

"To the best of our knowledge," wrote the four researchers, "this work represents the first all-optical control for holonomic quantum computation in solid-state quantum systems."


This research was funded by the National Key Basic R&D Program, China (No. 2013CB921804), National Key R&D Program, China (No. 2016YFA0301803 ), and Key Program of the Education Department of Anhui Province (No. KJ2015A299).

See the article: J. Zhou, B. J. Liu, Z. P. Hong, and Z. Y. Xue, Fast holonomic quantum computation based on solid-state spins with all-optical control, Sci. China-Phys. Mech. Astron. 61, 010312 (2018), http://engine.scichina.com/publisher/scp/journal/SCPMA/61/1/10.1007/s11433-017-9119-8?slug=full%20text

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