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Progress of Theoretical Physics

Realization of Quantum Communication by the Polarization of Photons

Akio Motoyoshi, Masaya Matsuoka

Published Aug 1, 1998• 3 citations
Publisher

Abstract

Making use of the polarization of photons, we present a new method to realize quantum communication using any qubit through a mixture or pure state as an ancilla.
DOI
10.1143/ptp.100.455

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Quantum polarization is an important property that has been extensively used for quantum communication purposes. In this work, the mixture of an unpolarized two-mode state and a two-mode pure state is analysed. This mixture is controlled by a single parameter, namely the degree of purity. The quantum polarization of the two-mode mixed state is discussed using the quantum Stokes parameters and the quantum degree of polarization. A relation between the degree of purity and the quantum degree of polarization is established. The mixture is used to model coherent light amplified by an erbium-doped fibre amplifier, which focuses the loss of polarization due to the unpolarized light resulting from spontaneous emission. Finally, the use of such a mixed state in the quantum key distribution using multiphoton pulses is analysed.