Practical quantum key distribution: On the security evaluation with inefficient single-photon detectors

Quantum Key Distribution with the BB84 protocol has been shown to be unconditionally secure even using weak coherent pulses instead of single-photon signals. The distances that can be covered by these methods are limited due to the loss in the quantum channel (e.g. loss in the optical fiber) and in the single-photon counters of the receivers. One can argue that the loss in the detectors cannot be changed by an eavesdropper in order to increase the covered distance. Here we show that the security analysis of this scenario is not as easy as is commonly assumed, since already two-photon processes allow eavesdropping strategies that outperform the known photon-number splitting attack. For this reason there is, so far, no satisfactory security analysis available in the framework of individual attacks.Comment: 11 pages, 6 figures; Abstract and introduction extended, Appendix added, references update

Basolateral and central amygdala differentially recruit and maintain dorsolateral striatum-dependent cocaine-seeking habits.

In the development of addiction, drug seeking becomes habitual and controlled by drug-associated cues, and the neural locus of control over behaviour shifts from the ventral to the dorsolateral striatum. The neural mechanisms underlying this functional transition from recreational drug use to drug-seeking habits are unknown. Here we combined functional disconnections and electrophysiological recordings of the amygdalo-striatal networks in rats trained to seek cocaine to demonstrate that functional shifts within the striatum are driven by transitions from the basolateral (BLA) to the central (CeN) amygdala. Thus, while the recruitment of dorsolateral striatum dopamine-dependent control over cocaine seeking is triggered by the BLA, its long-term maintenance depends instead on the CeN. These data demonstrate that limbic cortical areas both tune the function of cognitive territories of the striatum and thereby underpin maladaptive cocaine-seeking habits.This work was supported by the Fondation pour la Recherche Médicale (FRM), the United Kingdom Medical Research Council (MRC) Grant 9536855 to BJE, the AXA research fund to ABR, an INSERM Avenir and an Agence Nationale de la Recherche (ANR) grant ANR12 SAMA00201 to DB. Research was conducted within both the MRC/Wellcome Trust Behavioral and Clinical Neuroscience Institute of Cambridge and the Inserm team “Psychobiology of Compulsive Disorders”, University of Poitiers.This is the final version of the article. It was first available from NPG via http://dx.doi.org/10.1038/ncomms1008

Estimates for practical quantum cryptography

In this article I present a protocol for quantum cryptography which is secure against attacks on individual signals. It is based on the Bennett-Brassard protocol of 1984 (BB84). The security proof is complete as far as the use of single photons as signal states is concerned. Emphasis is given to the practicability of the resulting protocol. For each run of the quantum key distribution the security statement gives the probability of a successful key generation and the probability for an eavesdropper's knowledge, measured as change in Shannon entropy, to be below a specified maximal value.Comment: Authentication scheme corrected. Other improvements of presentatio

Practical free-space quantum key distribution over 1 km

A working free-space quantum key distribution (QKD) system has been developed and tested over an outdoor optical path of ~1 km at Los Alamos National Laboratory under nighttime conditions. Results show that QKD can provide secure real-time key distribution between parties who have a need to communicate secretly. Finally, we examine the feasibility of surface to satellite QKD.Comment: 5 pages, 2 figures, 2 tables. Submitted to Physics Review Letters, May 199

Daylight quantum key distribution over 1.6 km

Quantum key distribution (QKD) has been demonstrated over a point-to-point $\sim1.6$-km atmospheric optical path in full daylight. This record transmission distance brings QKD a step closer to surface-to-satellite and other long-distance applications.Comment: 4 pages, 2 figures, 1 table. Submitted to PRL on 14 January 2000 for publication consideratio

Long-distance Bell-type tests using energy-time entangled photons

Long-distance Bell-type experiments are presented. The different experimental challenges and their solutions in order to maintain the strong quantum correlations between energy-time entangled photons over more than 10 km are reported and the results analyzed from the point of view of tests of fundamental physics as well as from the more applied side of quantum communication, specially quantum key distribution. Tests using more than one analyzer on each side are also presented.Comment: 22 pages including 7 figures and 5 table

HYPERION: An open-source parallelized three-dimensional dust continuum radiative transfer code

HYPERION is a new three-dimensional dust continuum Monte-Carlo radiative transfer code that is designed to be as generic as possible, allowing radiative transfer to be computed through a variety of three-dimensional grids. The main part of the code is problem-independent, and only requires an arbitrary three-dimensional density structure, dust properties, the position and properties of the illuminating sources, and parameters controlling the running and output of the code. HYPERION is parallelized, and is shown to scale well to thousands of processes. Two common benchmark models for protoplanetary disks were computed, and the results are found to be in excellent agreement with those from other codes. Finally, to demonstrate the capabilities of the code, dust temperatures, SEDs, and synthetic multi-wavelength images were computed for a dynamical simulation of a low-mass star formation region. HYPERION is being actively developed to include new features, and is publicly available (http://www.hyperion-rt.org).Comment: Accepted for publication in Astronomy & Astrophysics. HYPERION is being prepared for release at the start of 2012, but you can already sign up to the mailing list at http://www.hyperion-rt.org to be informed once it is available for downloa

Quantum Cryptography

Quantum cryptography could well be the first application of quantum mechanics at the individual quanta level. The very fast progress in both theory and experiments over the recent years are reviewed, with emphasis on open questions and technological issues.Comment: 55 pages, 32 figures; to appear in Reviews of Modern Physic