Wavelength Selection for Satellite Quantum Key Distribution

Hearne, Shane (2023) Wavelength Selection for Satellite Quantum Key Distribution. Masters thesis, SETU Waterford.

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While the advancement of quantum computers threatens the security of current encryption methods, the satellite Quantum Key Distribution (QKD) channel is expected to enable global quantum communications. However, the availability of these systems is limited by background noise due to solar radiation and strong attenuation caused by turbulence and other adverse weather conditions. This work combines filtering techniques, adaptive optics, and optimal wavelength selection to permit daytime QKD through realistic atmospheric conditions. The secret key rate is determined using the decoy-state BB84-QKD protocol and used as a performance metric to investigate the performance of wavelengths ranging from the visible and near-infrared regions to the short-wave, mid-wave, and long-wave infrared regions of the electromagnetic spectrum. The satellite downlink channel is modelled to determine the signal gain accounting for diffraction-induced beam spread, extinction loss and turbulence-induced wavefront distortions while the background probability is calculated as a function of spectral radiance. Secret key rate optimization is a multivariate problem so a wavelength comparison cannot be done in isolation but instead requires a number of other parameters to be varied simultaneously. To this end, the secret key rate is determined for a range of wavelengths, receiver sizes and initial beam waists to reveal what combination achieves the best performance through a variety of atmospheric conditions. Additionally, satellite communications place physical limitations on transmitter and receiver sizes so the optimal wavelengths and secret key rates are determined for a number of incremental component size constraints.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Wavelength Selection, Satellite Quantum Key Distribution
Departments or Groups: *NONE OF THESE*
Divisions: School of Science > Department of Computing, Maths and Physics
Depositing User: Derek Langford
Date Deposited: 09 Jun 2023 14:22
Last Modified: 09 Jun 2023 14:22
URI: https://repository.wit.ie/id/eprint/7712

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