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Journal of Modern Optics

Quantum key distribution with continuous variables

Kamel Bencheikh, Thomas Symul, A. Jankovic, Juan Ariel Levenson

Published Nov 1, 2001• 34 citations
Publisher

Abstract

We study a new quantum cryptography protocol with continuous variables for the construction of secret quantum keys. The protocol is based on pairs of Einstein-Podolsky-Rosen entangled quadratures of a two-mode electromagnetic field generated by non-degenerate parametric amplification. Instantaneous measurements of the quantum fluctuations provide the random bits of the secret key. The irreversible alteration of the quadrature entanglement due to unauthorized measurements immunizes the quantum key distribution against eavesdropping attacks. Based on two identical non-degenerate parametric amplifiers, the protocol circumvents the usual 50% bits rejection due to base incompatibility during the key generation process, and avoids the need for homodyne detection schemes which are highly sensitive to the mode matching problems.

DOI
10.1080/09500340108240896

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We study a new quantum cryptography protocol with continuous variables for the construction of secret quantum keys. The protocol is based on pairs of Einstein-Podolsky-Rosen entangled quadratures of a two-mode electromagnetic field generated by non-degenerate parametric amplification. Instantaneous measurements of the quantum fluctuations provide the random bits of the secret key. The irreversible alteration of the quadrature entanglement due to unauthorized measurements immunizes the quantum key distribution against eavesdropping attacks. Based on two identical non-degenerate parametric amplifiers, the protocol circumvents the usual 50% bits rejection due to base incompatibility during the key generation process, and avoids the need for homodyne detection schemes which are highly sensitive to the mode matching problems.
We study a new quantum cryptography protocol with continuous variables for the construction of secret quantum keys. The protocol is based on pairs of Einstein-Podolsky-Rosen entangled quadratures of a two-mode electromagnetic field generated by non-degenerate parametric amplification. Instantaneous measurements of the quantum fluctuations provide the random bits of the secret key. The irreversible alteration of the quadrature entanglement due to unauthorized measurements immunizes the quantum key distribution against eavesdropping attacks. Based on two identical non-degenerate parametric amplifiers, the protocol circumvents the usual 50% bits rejection due to base incompatibility during the key generation process, and avoids the need for homodyne detection schemes which are highly sensitive to the mode matching problems.
Summary form only given. Quantum cryptography with continuous variables is an emerging field that consist in providing two communicating parties with a random secret key, using the quadrature components of electromagnetic fields as quantum carriers. According to quantum mechanics, the quantum states of the carriers used to establish the key are perturbed by the presence of unauthorized eavesdropping. Here, we present a new quantum cryptography protocol based on entangled quadratures of a two-mode electromagnetic field generated by phase sensitive parametric amplification (PSA).
A quantum secure communication protocol using correlations of continuous variable Einstein-Podolsky-Rosen (EPR) pairs is proposed. The proposed protocol may implement both quantum key distribution and quantum message encryption by using a nondegenerate optical parametric amplifier (NOPA). The general Gaussian-cloner attack strategy is investigated in detail by employing Shannon information theory. Results show that the proposed scheme is secure, which is guaranteed physically by the correlations of the continuous variable EPR entanglement pairs generated by the NOPA.
A new protocol realizing quantum key distribution for continuous variables is proposed, in which the bright entangled EPR beams are produced from a phase-sensitive nondegenerate optical parametric amplifier. Based on randomly changing the operating states of NOPA at the sending station and randomly choosing the phase difference between two modes of EPR beams at the receiving station, the secret key string is established. The application of direct detection system of photocurrents makes the proposed scheme relatively easier to be experimentally demonstrated.
We analyze the distribution of secure keys using quantum cryptography based on the continuous variable degree of freedom of entangled photon pairs. We derive the information capacity of a scheme based on the spatial entanglement of photons from a realistic source, and show that the standard measures of security known for quadrature-based continuous variable quantum cryptography (CV-QKD) are inadequate. A specific simple eavesdropping attack is analyzed to illuminate how secret information may be distilled well beyond the bounds of the usual CV-QKD measures.
In this paper, we present the first experimental demonstration on continuous variable quantum key distribution using determinant Einstein-Podolsky-Rosen entangled states of optical field. By means of the instantaneous measurements of the quantum fluctuations of optical modes, respectively, distributed at sender and receiver, the random bits of secret key are obtained without the need for signal modulation. The post-selection boundaries for the presented entanglement-based scheme against both Gaussian collective and individual attacks are theoretically concluded. The final secret key rates of 84 kbits/s and 3 kbits/s are completed under the collective attack for the transmission efficiency of 80% and 40%, respectively.