Homodyne detection of weak coherent optical pulse: Applications to quantum cryptography

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

A Prospective Study of Information -Theoretic and Practical Quantum Key Distribution

“…While sifting, the sender (Alice) and the receiver (Bob) should retain the states obtained while using a common basis, and discard the states with different bases. The added advantage is that the changing of the phase of the local oscillator permits the accessibility of both the quadratures to secure the signal against the squeezed state attacks and also to perform measurement in any of the basis as required [169,170,173]. (b) Dual Quadrature Homodyne Detection: In the dual mode of homodyne detection, both the quadratures are measured simultaneously.…”

“…In order to attain this, both the the local oscillator and the signal are split. One part of the oscillator is shifted in phase by 90°and the splitted signal is brought to interference with the local oscillator's signals which is detected in two balanced detectors [169,170,173]. No additional phase modulator on the local oscillator channel is required in this type of homodyne detection because only the oscillator frequency needs to be optically locked with the quantum signal.…”

Gaussian Quantum Trajectories for the Variational Simulation of Open Quantum-Optical Systems

“…In practical experimental settings, the use of homodyne detection schemes is paramount in a variety of systems. Notable examples are in quantum cryptography [79] and the detection of 'spooky action at a distance' [80].…”

Phase‐Locked Homodyne Measurement of Quasiprobability Q Function and Detection of Information‐Carrying Weak‐Coherent States

“…This scheme does not depend on computational algorithms, but on the quantum properties of the photons used for the key distribution, offering unconditional security. Among some proposals for the QKD receivers, there is the one based in photon counters; where the information is transmitted by manipulation of a single photon's properties, which implies the use of single‐photon sources and detectors; however, this detectors exhibit low quantum efficiency at the telecommunications wavelengths, besides working in Geiger mode requiring quenching; as a result the detector is limited to data rates up to 8 Mbps , which is a very low speed as compared to the requirements of present and future networks.…”