Agile quantum cryptography and non-classical state generation
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In the ﬁrst half of this Thesis, we introduce a framework of “quantum cryptographic agility,” which allows for a resource-efﬁcient swap of an underlying cryptographic protocol. Speciﬁcally, we introduce several schemes which perform the tasks of Digital Signatures and Secret Sharing. Our ﬁrst achievement is an investigation of Quantum Digital Signatures (QDS) over a continuous-variables platform, consisting of phase-encoded coherent states and heterodyne phase detection. QDS allows for secure authentication of a classical message, while guaranteeing message transferability. For the ﬁrst time, we prove security of CV QDS in the presence of an eavesdropper on the quantum channels. We then introduce a continuous variable (CV) Quantum Secret Sharing (QSS) protocol. Our security proof allows for classical information to be split and shared between multiple potentially dishonest recipients, while retaining security against collective beamsplitter and entangling-cloner attacks. In the last chapter of this half, we introduce another QDS scheme which runs over identical hardware setup to our QSS protocol. We analyse experimental data in which quantum coherent states were distributed at a rate of 1 GHz, which for QDS allows us to securely sign a message in less than 0.05 ms. In the second half of this Thesis we suggest and discuss a deterministic source of nonclassical light, which we call “PhoG”. Our source is based on the coherent diffusive photonics, relying on both coherent and dissipative evolution of the quantum state, and may be realised in an array of dissipatively-coupled laser-inscribed waveguides in a χ⁽³⁾ glass. We analyse the PhoG device with several analytical and numerical models and demonstrate that a coherent state input leads to a bright output state with strong photon-number squeezing. With minor reconﬁguration our system can generate entanglement between spatially separated modes via a process analogous to four-wave mixing.
Thesis, PhD Doctor of Philosophy
Description of related resourcesAgile quantum cryptography and non-classical state generation (thesis data) Thornton, M., University of St Andrews, 2020. DOI: https://doi.org/10.17630/6ba10862-4bdd-478f-8bd7-4f4b4d383374
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