Thesis

A comprehensive decoy-state quantum key distribution model for practical single photon sources

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Awarding institution
  • University of Strathclyde
Date of award
  • 2026
Thesis identifier
  • T18108
Person Identifier (Local)
  • 202080754
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • The most widely used quantum key distribution (QKD) protocol has been the Bennett- Brassard 1984 (BB84). Practical quantum sources that reach ideal single-photon emission behaviour do not presently exist, making them vulnerable to photon number splitting (PNS) attacks. Weak coherent pulses (WCPs) are favoured in QKD for their feasibility and cost-effectiveness. The exploitable multiphoton emissions of WCPs have rendered the decoy method, which is essential to prevent PNS attacks while offering key rate enhancement. Seeking potential key-rate and finite-block scaling advantages in BB84, we evaluate high brightness, low-g(2)(0) single-photon sources (SPSs) as alternative QKD sources, given their low multiphoton contributions. The challenge lies in their diverse quantum-mechanical systems, lacking a generic statistical distribution for their photon emissions. Researchers often assume distributions that do not accurately represent the SPS statistics, hence we propose a partial characterisation of the SPS using the time-zero second-order correlation function and the mean photon number to estimate secure keys for our non-decoy SPS protocol, where we introduce tight finite key bounds based on decoy WCP techniques. This approach drastically reduces the required block sizes to approach the asymptotic key rates and shows SPSs’ potential for key enhancement in short-range QKD networks. We also present two decoy SPS methods, deriving novel security bounds of the yields and relaxing previous assumptions on arbitrary distributions. These methods highlight the necessary SPS characteristics to surpass decoy WCP. Finally, we implement our non-decoy SPS protocol in our satellite-to-ground QKD model, identifying the optimal wavelength and estimating the annual key volume for our non-decoy SPS, based on a 2D material defect, and for a 2-decoy WCP protocol.
Advisor / supervisor
  • Oi, Daniel K. L.
  • Jeffers, John
Resource Type
DOI
Date Created
  • 2024

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