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Public Seminar of RPg Student:
Improving Classical and Quantum Free-Space Communication by Adaptive Optics

Speaker:Mr. Kai Sum CHAN
Affiliation:The University of Hong Kong
Date:June 16, 2021 (Wednesday)
Time:9:30 a.m.
Venue:Room 522, 5/F, Chong Yuet Ming Physics Building, HKU


The optical free-space communication is affected by atmospheric turbulence. The optical signal is distorted by the inhomogeneous refractive index media which cause by the fluctuation of air density, pressure, and temperature. When the wave passes through such media, its wavefront deviates nonuniformly. This causes a serious problem for systems that encode information in the phase, such as Phase-Shift Keying (PSK) modulation in classical communication and Time-bin Encoding in quantum communication. Also, for Measurement-Device-Independent Quantum Key Distribution(MDI-QKD), the random phase fluctuation reduces the visibility of the Hong-Ou-Mandel(HOM) interference. Here we proposed a novel method to compensate for the signal distortion using Adaptive Optics(AO). AO has been used for astronomical observations and classical optics communication. However, most of the proposed methods are ineffective with quantum communication. Our invention is expected to enable both classical and quantum free-space communication to compensate for the atmospheric distortion and increase the information transmission rate. The phase-screens simulation will be used to verify the effectiveness of the system.

Anyone interested is welcome to attend.