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Theoretical study of continuous-variable quantum key distribution

Abstract : This thesis is concerned with quantum key distribution (QKD), a cryptographic primitive allowing two distant parties, Alice and Bob, to establish a secret key, in spite of the presence of a potential eavesdropper, Eve. Here, we focus on continuous-variable protocols, for which the information is coded in phase-space. The main advantage of these protocols is that their implementation only requires standard telecom components. The security of QKD lies on the laws of quantum physics: an eavesdropper will necessary induce some noise on the communication, therefore revealing her presence. A particularly difficult step of continuous-variable QKD protocols is the ''reconciliation'' where Alice and Bob use their classical measurement results to agree on a common bit string. We first develop an optimal reconciliation algorithm for the initial protocol, then introduce a new protocol for which the reconciliation problem is automatically taken care of thanks to a discrete modulation. Proving the security of continuous-variable QKD protocols is a challenging problem because these protocols are formally described in an infinite dimensional Hilbert space. A solution is to use all available symmetries of the protocols. In particular, we introduce and study a class of symmetries in phase space, which is particularly relevant for continuous-variable QKD. Finally, we consider finite size effects for these protocols. We especially analyse the influence of parameter estimation on the performance of continuous-variable QDK protocols.
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Contributor : Anthony Leverrier <>
Submitted on : Thursday, January 28, 2010 - 12:31:02 AM
Last modification on : Wednesday, September 16, 2020 - 5:43:40 PM
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  • HAL Id : tel-00451021, version 1

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Anthony Leverrier. Theoretical study of continuous-variable quantum key distribution. Atomic Physics [physics.atom-ph]. Télécom ParisTech, 2009. English. ⟨tel-00451021⟩

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