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Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR)

An experimental quantum cryptography using balanced homodyne detection over a 1 km optical fiber

Ryo Namiki, T. Konishi, H. Yanianaka, 辰哉 三尋木, Takuya Hirano

Published Nov 13, 2002• 3 citations
Publisher

Abstract

We report an experimental quantum cryptography using balanced homodyne detection over a 1 km optical fiber. In this scheme we can measure the distribution of the quadrature amplitudes of the weak coherent pulse.
DOI
10.1109/cleopr.2001.971007

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Abstract We propose a quantum key distribution system using balanced homodyne detection, in which strong reference pulses are time‐multiplexed with weak signal pulses by means of fiber interferometer. We use a dual‐threshold decision scheme for postdetection to improve the system performance in terms of BER, with a trade‐off in effective key generation rate. We conduct experimental measurements at 64 km SMF fiber at 1550 nm wavelength, and we prove that the system security can also be enhanced with properly selected threshold parameters. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1934–1939, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24471
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A balanced homodyne detection scheme with nanosecond time resolution and sub-shot-noise sensitivity has been developed and successfully tested yielding an efficient detection scheme for high-speed quantum-optical measurements and communication protocols, for example, quantum cryptography. The parameters of the detector and its precise balancing allow complete characterization of quantum states created by femtosecond light pulses that include the measurement of photon number, optical phase, and statistical properties with a high signal-to-noise ratio for the whole bandwidth from DC to several tens of megahertz. The electronic part of the detector is based on a commercially available amplifier that provides ease of construction and use while yielding good performance.