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

Male Antarctic fur seals: neglected food competitors of bioindicator species in the context of an increasing Antarctic krill fishery.

The fishery for Antarctic krill is currently managed using a precautionary, ecosystem-based approach to limiting catch, with performance indices from a long-term monitoring program focused on several krill-dependent predators that are used to track ecosystem health. Concerns over increased fishing in concentrated areas and ongoing efforts to establish a Marine Protected Area along the Peninsula, a key fishing region, is driving the development of an adaptive management system for the fishery. The cumulative effects of fishing effort and interactions among krill-dependent predators and their performance is at present neglected in the CCAMLR Ecosystem Monitoring Program. However, we show considerable overlap between male Antarctic fur seals and the krill fishery in a complex mosaic, suggesting potential for cumulative impacts on other krill dependent predators. A holistic view is required as part of future efforts to manage the krill fishery that incorporates various sources of potential impacts on the performance of bioindicator species, including the fishery and its interactions with various krill dependent predators. © 2020, The Author(s)

Hacking commercial quantum cryptography systems by tailored bright illumination

The peculiar properties of quantum mechanics allow two remote parties to communicate a private, secret key, which is protected from eavesdropping by the laws of physics. So-called quantum key distribution (QKD) implementations always rely on detectors to measure the relevant quantum property of single photons. Here we demonstrate experimentally that the detectors in two commercially available QKD systems can be fully remote-controlled using specially tailored bright illumination. This makes it possible to tracelessly acquire the full secret key; we propose an eavesdropping apparatus built of off-the-shelf components. The loophole is likely to be present in most QKD systems using avalanche photodiodes to detect single photons. We believe that our findings are crucial for strengthening the security of practical QKD, by identifying and patching technological deficiencies.Comment: Revised version, rewritten for clarity. 5 pages, 5 figures. To download the Supplementary information (which is in open access), go to the journal web site at http://dx.doi.org/10.1038/nphoton.2010.21

Effect of Age and Level of Education on Neurocognitive Impairment in HIV Positive Zambian Adults

Objective: Older age and lower education levels are known to be associated with worse neurocognitive (NC) performance in healthy adults, and individuals with HIV infection may experience accelerated brain/cognition aging. However, higher education may possibly protect against HIV-associated neurocognitive disorders (HAND). The aim of the current cross-sectional study was to assess the effect of age and education in an HIV-1 clade C infected adult population in urban Zambia. Method: Demographically corrected Zambian norms on a neuropsychological (NP) test battery were used to correct for normal age and education effects. The study assessed 286 HIV positive (+) males (37.1%) and females (62.9%) with a mean age of 41.35 (SD = 8.56) and mean years of education = 10.16 (SD = 2.18). A comprehensive NP test battery was used to assess cognitive domains frequently affected by HIV: attention/working memory, learning/and delayed recall, executive function, verbal fluency, processing speed, verbal and visual episodic memory, and fine motor skills. Results: In younger HIV+ Zambians, higher education evidenced protective effects against NC impairments overall, and for the specific domains of executive functions, learning and speed of information processing. Impairment scores did not support accelerated overall brain aging although the restricted age range and relative youth of our total sample may have precluded detection of such tendencies. Conclusions: The present study raises the need to investigate factors that could be implicated in the poor neurocognitive performance among the younger, less educated HIV+ individuals in Zambia.Effect of Age and Level of Education on Neurocognitive Impairment in HIV Positive Zambian AdultspublishedVersio

Superlinear threshold detectors in quantum cryptography

We introduce the concept of a superlinear threshold detector, a detector that has a higher probability to detect multiple photons if it receives them simultaneously rather than at separate times. Highly superlinear threshold detectors in quantum key distribution systems allow eavesdropping the full secret key without being revealed. Here, we generalize the detector control attack, and analyze how it performs against quantum key distribution systems with moderately superlinear detectors. We quantify the superlinearity in superconducting single-photon detectors based on earlier published data, and gated avalanche photodiode detectors based on our own measurements. The analysis shows that quantum key distribution systems using detector(s) of either type can be vulnerable to eavesdropping. The avalanche photodiode detector becomes superlinear towards the end of the gate, allowing eavesdropping using trigger pulses containing less than 120 photons per pulse. Such an attack would be virtually impossible to catch with an optical power meter at the receiver entrance.Comment: Rewritten for clearity. Included a discussion on detector dark counts, a discussion on how to tackle this type of loopholes, and updated references. 8 pages, 6 figure

Experimental demonstration of phase-remapping attack in a practical quantum key distribution system

Unconditional security proofs of various quantum key distribution (QKD) protocols are built on idealized assumptions. One key assumption is: the sender (Alice) can prepare the required quantum states without errors. However, such an assumption may be violated in a practical QKD system. In this paper, we experimentally demonstrate a technically feasible "intercept-and-resend" attack that exploits such a security loophole in a commercial "plug & play" QKD system. The resulting quantum bit error rate is 19.7%, which is below the proven secure bound of 20.0% for the BB84 protocol. The attack we utilize is the phase-remapping attack (C.-H. F. Fung, et al., Phys. Rev. A, 75, 32314, 2007) proposed by our group.Comment: 16 pages, 6 figure

Niches of marine mammals in the European Arctic

The Arctic is warming rapidly, with concomitant sea ice losses and ecosystem changes. The animals most vulnerable to Arctic food web changes are long-lived and slow-growing such as marine mammals, which may not be able to adapt rapidly enough to respond to changes in their resource bases. To determine the current extent and sources of these resource bases, we examined isotopic and trophic niches for marine mammals in the European Arctic using skin carbon (δ13C) and nitrogen (δ 15N) stable isotope (SI) compositions from 10 species: blue, fin, humpback, minke, sperm and white whales, bearded and ringed seals, walruses and polar bears, and dietary fatty acids (FAs) in polar bears, walruses and most of the whale species listed here. SI values showed clear species separation by trophic behaviour and carbon sources. Bearded seals, walruses and white whales had the smallest isotopic niches; these species are all resident High Arctic species and are likely to be particularly vulnerable to changes in Arctic ecosystems. We found clear separation between FA groupings driven by pelagic, benthic and planktonic/algal sources: pelagic FAs in all whales, benthic FAs in walruses, and copepod/algae/dinoflagellate FAs in polar bears, with some polar bear compositions approaching those of the whales and walruses. There is strong niche partitioning between study species with minimal functional redundancy, which could impact Arctic ecosystem structure and connectivity if populations of these large nutrient vectors are reduced or lost

Effect of Intensity Modulator Extinction on Practical Quantum Key Distribution System

We study how the imperfection of intensity modulator effects on the security of a practical quantum key distribution system. The extinction ratio of the realistic intensity modulator is considered in our security analysis. We show that the secret key rate increases, under the practical assumption that the indeterminable noise introduced by the imperfect intensity modulator can not be controlled by the eavesdropper.Comment: 6 pages, 5 figures. EPJD accepte