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Imaging and Applied Optics

Free Space Quantum Communication using Continuous Polarization Variables

Bettina Heim, Christian Peuntinger, Christoffer Wittmann, Christoph Marquardt, Gerd Leuchs

Published Jan 1, 2011• 6 citations
Publisher

Abstract

We experimentally investigate atmospheric influences on quantum communication using continuous polarization variables. Signal and local oscillator are combined in one spatial mode, which leads to excellent interference at the homodyne detection. Phase fluctuations are thus auto-compensated.
DOI
10.1364/lsc.2011.lwd3

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Free space QKD over an atmospheric channel was demonstrated in 1996 for the first time. Since then, several prepare-and-measure and entanglement-based schemes have been implemented (for a detailed overview, see). All of these systems use single-photon detectors, and therefore have to employ spatial, spectral and/or temporal filtering in order to reduce background light. In our system, we use an alternative approach: with the help of a bright local oscillator (LO), we perform homodyne measurements on weak coherent polarization states.
Abstract In Discrete Variable Quantum Key Distribution (DV-QKD), the homodyne detection method is frequently employed for its simplicity in use, effectiveness in terms of error correction, and suitability with contemporary optical communication systems. Being a coherent detection method, it relies on a local oscillator whose frequency is matched to that of the transmitted carrier's signal. In this paper, we evaluate a Free Space Optical (FSO) DV-QKD system based on the KMB09 protocol using Homodyne detection under random phase fluctuation and depolarizing noise error. We present simulation results for System Efficiency and Quantum Bit Error Rate (QBER) for the proposed model. An obtained efficiency ({25%25\%25%}) for our proposed DV-QKD system model shows that under atmospheric turbulence and noise effect and it is in line with the available analytical results. However, the inclusion of random phase fluctuation and noise led to higher-than-normal QBER which is anticipated in a real-world scenario.