Secure gated detection scheme for quantum cryptography

Several attacks have been proposed on quantum key distribution systems with gated single-photon detectors. The attacks involve triggering the detectors outside the center of the detector gate, and/or using bright illumination to exploit classical photodiode mode of the detectors. Hence a secure detection scheme requires two features: The detection events must take place in the middle of the gate, and the detector must be single-photon sensitive. Here we present a technique called bit-mapped gating, which is an elegant way to force the detections in the middle of the detector gate by coupling detection time and quantum bit error rate. We also discuss how to guarantee single-photon sensitivity by directly measuring detector parameters. Bit-mapped gating also provides a simple way to measure the detector blinding parameter in security proofs for quantum key distribution systems with detector efficiency mismatch, which up until now has remained a theoretical, unmeasurable quantity. Thus if single-photon sensitivity can be guaranteed within the gates, a detection scheme with bit-mapped gating satisfies the assumptions of the current security proofs.Comment: 7 pages, 3 figure

Comment on "Resilience of gated avalanche photodiodes against bright illumination attacks in quantum cryptography"

This is a comment on the publication by Yuan et al. [Appl. Phys. Lett. 98, 231104 (2011); arXiv:1106.2675v1 [quant-ph]].Comment: 2 page

A reliability study of the rapid emergency triage and treatment system for children

Background To evaluate inter- and intrarater reliability of a new Scandinavian triage system for children, the Rapid Emergency Triage and Treatment System-pediatric (RETTS-p). Methods Two observational studies were conducted at the Pediatric Emergency Department (PED), St. Olav’s University Hospital, Trondheim, Norway. Using RETTS-p, nurses assign one of five triage priority levels to each patient on the basis of clinical signs and symptoms evaluations and vital parameter measurements. Study 1: Prior to the introduction of RETTS-p in 2012, all nurses in the PED completed a theoretical and practical training. Four months later, 19 nurses triaged 20 fictive but realistic pediatric cases two times 9 months apart (Waves A and B). Study 2: Nurse pairs consisting of a regular nurse and a research nurse simultaneously and independently triaged 200 pediatric patients who were referred with various common medical and surgical complaints. Results Study 1: Kendall’s W for Waves A and B were 0.822 and 0.844, respectively. Using a mixed linear model, we found no difference in triage priority levels between Waves A and B. Compared to a consensus level made by the research group, the nurses rated 85.1 % fictive cases correctly, and 99 % were rated correctly or within one adjacent priority score. Study 2: The interrater correlation coefficient in a linear mixed model was 0.762, confirming a high interrater reliability in real-life triaging. Discussion We found a very high degree of agreement between nurses who used RETTS-p to prioritize children, both in a theoretical case scenarios study, but also in real-life triaging. Conclusions RETTS-p may be a credible and robust triage system, but it has not been validated yet.This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://​creativecommons.​org/​licenses/​by/​4.​0/​), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://​creativecommons.​org/​publicdomain/​zero/​1.​0/​) applies to the data made available in this article, unless otherwise stated

Avoiding the Detector Blinding Attack on Quantum Cryptography

We show the detector blinding attack by Lydersen et al [1] will be ineffective on most single photon avalanche photodiodes (APDs) and certainly ineffective on any detectors that are operated correctly. The attack is only successful if a redundant resistor is included in series with the APD, or if the detector discrimination levels are set inappropriately

Thermal blinding of gated detectors in quantum cryptography

It has previously been shown that the gated detectors of two commercially available quantum key distribution (QKD) systems are blindable and controllable by an eavesdropper using continuous-wave illumination and short bright trigger pulses, manipulating voltages in the circuit [L. Lydersen et al., Nat. Photonics DOI:10.1038/nphoton.2010.214]. This allows for an attack eavesdropping the full raw and secret key without increasing the quantum bit error rate (QBER). Here we show how thermal effects in detectors under bright illumination can lead to the same outcome. We demonstrate that the detectors in a commercial QKD system Clavis2 can be blinded by heating the avalanche photo diodes (APDs) using bright illumination, so-called thermal blinding. Further, the detectors can be triggered using short bright pulses once they are blind. For systems with pauses between packet transmission such as the plug-and-play systems, thermal inertia enables Eve to apply the bright blinding illumination before eavesdropping, making her more difficult to catch.Comment: 10 pages, 12 figure

Franchise i dagligvarebransjen : hvilke forskjeller finnes i franchisesystemene i Rema 1000 og Ica Norge, og kan disse forskjellene forklare hvorfor det har oppstått misnøye og internt bråk i én av kjedene?

Denne oppgaven tar for seg forskjeller i franchisesystemene til Rema 1000 og Ica Norge, for å forklare hvorfor det er intern misnøye og bråk i den ene kjeden og hvorfor vi ikke ser det i den andre. Vi fant med utgangspunkt i intervjuer med kjøpmenn fra begge kjedene at det er store forskjeller mellom de ulike franchisesystemene, der noen forskjeller var viktigere enn andre til å forklare hvorfor misnøye og bråk oppstår. De forskjellene vi har sett på er faglig og sosialt miljø, franchisekontrakten, samarbeid og kommunikasjon med ledelsen, i hvilken grad kjøpmennene er fornøyd med kjeden sin, og hvordan franchisesystemene fungerer i praksis. Ut ifra våre analyser har vi funnet ut at de faktorene som er mest utslagsgivende for hvordan trivselen er blant franchisetakerne er samarbeidet mellom partene i kjeden, herunder kommunikasjon, grad av tillitt til ledelsen og konsekvensene av økonomien i kjeden. Disse faktorene bestemmer derfor i hvilken grad det vil kunne oppstå internt bråk og klager fra franchisetakerne