Quantum key distribution beyond the repeaterless secret key capacity
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Authors
Minder, Mariella
Advisors
Date
2020-08-24Awarding Institution
University of Cambridge
Qualification
Doctor of Philosophy (PhD)
Type
Thesis
Metadata
Show full item recordCitation
Minder, M. (2020). Quantum key distribution beyond the repeaterless secret key capacity (Doctoral thesis). https://doi.org/10.17863/CAM.62170
Abstract
Quantum communications promise to provide information theoretic security in the exchange of information. However, unlike their classical counterpart, they utilise dim optical pulses whose amplification is prohibited. Consequently, their transmission rate and range is confined below a theoretical limit known as repeaterless secret key capacity. Overcoming this limit with today’s technology was believed to be impossible until the recent proposal of Twin-field (TF) quantum key distribution (QKD), a scheme that uses phase-coherent optical signals and an auxiliary measuring station to distribute quantum information. Here, TF-QKD and its main variations are initially explored and compared in simulations, to assess their performance in different attributes. Such schemes are also practically implemented for the first time in two experiments. The first is a proof-of-principle implementation over significant channel losses, in excess of 90 dB. In the second, the setup is developed further and the protocol is implemented over real fibre channels exceeding 600 km in length, representing the first fibre-based secure quantum communication beyond the barriers of 600 km and 100 dB. In both cases, in the high loss/distance regime, the resulting secure key rates exceed the repeaterless secret key capacity, a result never achieved before.
Keywords
quantum cryptography, quantum key distribution, interferometry, phase stabilisation, fibre optics
Sponsorship
EPSRC, Toshiba Research Europe
Identifiers
This record's DOI: https://doi.org/10.17863/CAM.62170
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