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Contribution à l'étude et à la réalisation d'un système de distribution quantique de clef par codage en phase

Authors
  • Agnolini, Sébastien
Publication Date
Apr 23, 2007
Source
HAL
Keywords
Language
English
License
Unknown
External links

Abstract

The security of communication systems is based on key cryptography techniques. Communications on a protected channel impose the exchange of a key between Alice and Bob. Eve, a third actor in the scene tries to obtain this key without making her presence notorious to the others. The quantum security results from the impossibility to Eve to duplicate successfully signals or to extract a significant part of them without giving evidence of her intervention. Since her intervention introduces important changes in the error rate of the signals received by Bob. These errors result from incompatible observations of the same quantum object, as well as phase measurements of a single photon coded on two different basis. A weak rate of error guarantees confidentiality of the key. The protocol BB84 authorizes the elaboration and the exchange of key between Alice and Bob, it requires four quantum states forming two basis, called A1 and A2 containing two symbols, named 0 and 1, each. The A1 and A2 bases are conjugated. This thesis presents for consideration a research and an experimental realization of a quantum key distribution system using the protocol BB84 by coding in phase on a single photon at l = 1,5 µm. The generation of this single photon is assured by an ILM laser. The optical pulses are strongly attenuated. The QPSK modulation satisfies independent choices of base and symbol assured by dual-electrode Mach-Zehnder modulators. Three coherent detection schemes are proposed and compared. The successive modifications to our system take to propose a one optical way quantum key distribution scheme by DQPSK coding.

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