Topological quantum simulation implementation based on vortex photons in degenerative cavities

Li Chuanfeng, Xu Jinshi, Han Yongjian and others from the team of academicians Guo Guangcan of the University of Science and Technology of China bound photons (also known as vortex photons) carrying different orbital angular momentum in a degenerate optical resonant cavity, and artificially synthesized a one-dimensional topological lattice by introducing the spin orbit coupling of photons, creating a new method for topological quantum simulation. The results of the research were published in Nature Communications on April 19.


Schematic diagram of experimental apparatus and theoretical model: a. Degenerate optical resonator b. Synthetic photon orbital angular momentum lattice Courtesy of The University of Science and Technology of China

Dimension is an important physical quantity that determines the properties of matter in the universe. However, in scientific research, due to the limitations of the three-dimensional physical world, it is often difficult to study the properties and evolutionary characteristics of physical systems above three dimensions. In response to this problem, the researchers proposed that it can be solved by artificially synthesizing dimensions. For example, by introducing two synthetic dimensions into a three-dimensional system, it is possible to study the physical properties of five dimensions on that system.

The number of orbital angular momentum carried by vortex photons can be theoretically unlimited, making it an ideal carrier for constructing synthetic dimensions. In 2015, the research group of Professor Zhou Zhengwei of the Key Laboratory of Quantum Information of the Chinese Academy of Sciences proposed for the first time a scheme for quantum simulation based on the angular momentum dimension of synthetic photon orbits.

On the basis of previous research, Li Chuanfeng, Xu Jinshi, etc. creatively introduced anisotropic liquid crystal phase sheets in the standing wave degeneracy cavity to achieve the coupling of vortex photon orbital angular momentum and photon spin (i.e., polarization) in the cavity. The orbital angular momentum carried by the photons in the cavity is integer discrete, corresponding to a one-dimensional discrete lattice. Thus, photons carrying different orbital angular momentum can be equivalent to quasiparticles located at different lattice lattice points, and photons with different orbital angular momentum are coupled by spin degrees of freedom, thereby simulating the back-and-forth transition of particles between different lattice lattice points.

Using the resonance energy spectrum detection technology, the research team directly characterized the state density and band structure of the spin-orbit coupling system. Using the excellent tunable properties of the experimental device, the research team clearly demonstrated the evolution of the periodic drive system with open and closed bands. The research team further introduced different evolutionary timings, systematically studied the characteristics of different topologies and detected topological windings.

The reviewers believe that “this work proposes a new mechanism for using the intrinsic spin and orbital angular momentum of photons as synthetic dimensions, thus providing new possibilities for the study of rich topological physical properties in the cavity.” (Source: China Science Daily Wang Min)

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