13,030 research outputs found
Quantum cryptography: key distribution and beyond
Uniquely among the sciences, quantum cryptography has driven both
foundational research as well as practical real-life applications. We review
the progress of quantum cryptography in the last decade, covering quantum key
distribution and other applications.Comment: It's a review on quantum cryptography and it is not restricted to QK
Practical Evaluation of Security for Quantum Key Distribution
Many papers proved the security of quantum key distribution (QKD) system, in
the asymptotic framework. The degree of the security has not been discussed in
the finite coding-length framework, sufficiently. However, to guarantee any
implemented QKD system requires, it is needed to evaluate a protocol with a
finite coding-length. For this purpose, we derive a tight upper bound of the
eavesdropper's information. This bound is better than existing bounds. We also
obtain the exponential rate of the eavesdropper's information. Further, we
approximate our bound by using the normal distribution.Comment: The manuscript has been modfie
Trusted Noise in Continuous-Variable Quantum Key Distribution: a Threat and a Defense
We address the role of the phase-insensitive trusted preparation and
detection noise in the security of a continuous-variable quantum key
distribution, considering the Gaussian protocols on the basis of coherent and
squeezed states and studying them in the conditions of Gaussian lossy and noisy
channels. The influence of such a noise on the security of Gaussian quantum
cryptography can be crucial, even despite the fact that a noise is trusted, due
to a strongly nonlinear behavior of the quantum entropies involved in the
security analysis. We recapitulate the known effect of the preparation noise in
both direct and reverse-reconciliation protocols, as well as the detection
noise in the reverse-reconciliation scenario. As a new result, we show the
negative role of the trusted detection noise in the direct-reconciliation
scheme. We also describe the role of the trusted preparation or detection noise
added at the reference side of the protocols in improving the robustness of the
protocols to the channel noise, confirming the positive effect for the
coherent-state reverse-reconciliation protocol. Finally, we address the
combined effect of trusted noise added both in the source and the detector.Comment: 25 pages, 9 figure
Distributing Secret Keys with Quantum Continuous Variables: Principle, Security and Implementations
The ability to distribute secret keys between two parties with
information-theoretic security, that is, regardless of the capacities of a
malevolent eavesdropper, is one of the most celebrated results in the field of
quantum information processing and communication. Indeed, quantum key
distribution illustrates the power of encoding information on the quantum
properties of light and has far reaching implications in high-security
applications. Today, quantum key distribution systems operate in real-world
conditions and are commercially available. As with most quantum information
protocols, quantum key distribution was first designed for qubits, the
individual quanta of information. However, the use of quantum continuous
variables for this task presents important advantages with respect to qubit
based protocols, in particular from a practical point of view, since it allows
for simple implementations that require only standard telecommunication
technology. In this review article, we describe the principle of
continuous-variable quantum key distribution, focusing in particular on
protocols based on coherent states. We discuss the security of these protocols
and report on the state-of-the-art in experimental implementations, including
the issue of side-channel attacks. We conclude with promising perspectives in
this research field.Comment: 21 pages, 2 figures, 1 tabl
Gaussian Quantum Information
The science of quantum information has arisen over the last two decades
centered on the manipulation of individual quanta of information, known as
quantum bits or qubits. Quantum computers, quantum cryptography and quantum
teleportation are among the most celebrated ideas that have emerged from this
new field. It was realized later on that using continuous-variable quantum
information carriers, instead of qubits, constitutes an extremely powerful
alternative approach to quantum information processing. This review focuses on
continuous-variable quantum information processes that rely on any combination
of Gaussian states, Gaussian operations, and Gaussian measurements.
Interestingly, such a restriction to the Gaussian realm comes with various
benefits, since on the theoretical side, simple analytical tools are available
and, on the experimental side, optical components effecting Gaussian processes
are readily available in the laboratory. Yet, Gaussian quantum information
processing opens the way to a wide variety of tasks and applications, including
quantum communication, quantum cryptography, quantum computation, quantum
teleportation, and quantum state and channel discrimination. This review
reports on the state of the art in this field, ranging from the basic
theoretical tools and landmark experimental realizations to the most recent
successful developments.Comment: 51 pages, 7 figures, submitted to Reviews of Modern Physic
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