20 research outputs found
Photon Counting OTDR : Advantages and Limitations
We give detailed insight into photon counting OTDR (nu-OTDR) operation,
ranging from Geiger mode operation of avalanche photodiodes (APD), analysis of
different APD bias schemes, to the discussion of OTDR perspectives. Our results
demonstrate that an InGaAs/InP APD based nu-OTDR has the potential of
outperforming the dynamic range of a conventional state-of-the-art OTDR by 10
dB as well as the 2-point resolution by a factor of 20. Considering the trace
acquisition speed of nu-OTDRs, we find that a combination of rapid gating for
high photon flux and free running mode for low photon flux is the most
efficient solution. Concerning dead zones, our results are less promising.
Without additional measures, e.g. an optical shutter, the photon counting
approach is not competitive.Comment: 12 pages, 13 figures, accepted for publication by IEEE Journal of
Lightwave Technolog
Testing random-detector-efficiency countermeasure in a commercial system reveals a breakable unrealistic assumption
In the last decade, efforts have been made to reconcile theoretical security
with realistic imperfect implementations of quantum key distribution (QKD).
Implementable countermeasures are proposed to patch the discovered loopholes.
However, certain countermeasures are not as robust as would be expected. In
this paper, we present a concrete example of ID Quantique's
random-detector-efficiency countermeasure against detector blinding attacks. As
a third-party tester, we have found that the first industrial implementation of
this countermeasure is effective against the original blinding attack, but not
immune to a modified blinding attack. Then, we implement and test a later full
version of this countermeasure containing a security proof [C. C. W. Lim et
al., IEEE Journal of Selected Topics in Quantum Electronics, 21, 6601305
(2015)]. We find that it is still vulnerable against the modified blinding
attack, because an assumption about hardware characteristics on which the proof
relies fails in practice.Comment: 12 pages, 12 figure
High resolution optical time domain reflectometer based on 1.55um up-conversion photon-counting module
We implement a photon-counting Optical Time Domain Reflectometer (OTDR) at
1.55um which exhibits a high 2-point resolution and a high accuracy. It is
based on a low temporal-jitter photon-counting module at 1.55um. This detector
is composed of a periodically poled Lithium niobate (PPLN) waveguide, which
provides a wavelength conversion from near infrared to visible light, and a low
jitter silicon photon-counting detector. With this apparatus, we obtain
centimetre resolution over a measurement range of tens of kilometres.Comment: 6 pages, 4 figure
Attacks exploiting deviation of mean photon number in quantum key distribution and coin tossing
The security of quantum communication using a weak coherent source requires
an accurate knowledge of the source's mean photon number. Finite calibration
precision or an active manipulation by an attacker may cause the actual emitted
photon number to deviate from the known value. We model effects of this
deviation on the security of three quantum communication protocols: the
Bennett-Brassard 1984 (BB84) quantum key distribution (QKD) protocol without
decoy states, Scarani-Acin-Ribordy-Gisin 2004 (SARG04) QKD protocol, and a
coin-tossing protocol. For QKD, we model both a strong attack using technology
possible in principle, and a realistic attack bounded by today's technology. To
maintain the mean photon number in two-way systems, such as plug-and-play and
relativistic quantum cryptography schemes, bright pulse energy incoming from
the communication channel must be monitored. Implementation of a monitoring
detector has largely been ignored so far, except for ID Quantique's commercial
QKD system Clavis2. We scrutinize this implementation for security problems,
and show that designing a hack-proof pulse-energy-measuring detector is far
from trivial. Indeed the first implementation has three serious flaws confirmed
experimentally, each of which may be exploited in a cleverly constructed
Trojan-horse attack. We discuss requirements for a loophole-free implementation
of the monitoring detector.Comment: 15 pages, 13 figures, Improved Introduction and Conclusion, Published
in Physical Review A, Accepted at QCrypt 2014, 4th international conference
on quantum cryptography, September 1-5, 2014 in Paris, France
http://2014.qcrypt.net/program
Demonstration of In Silico docking at a large scale on grid infrastructure
présenté par N. Jac
Grid enabled virtual screening against malaria
34 pages, 5 figures, 3 tables, to appear in Journal of Grid Computing - PCSV, à paraître dans Journal of Grid ComputingWISDOM is an international initiative to enable a virtual screening pipeline on a grid infrastructure. Its first attempt was to deploy large scale in silico docking on a public grid infrastructure. Protein-ligand docking is about computing the binding energy of a protein target to a library of potential drugs using a scoring algorithm. Previous deployments were either limited to one cluster, to grids of clusters in the tightly protected environment of a pharmaceutical laboratory or to pervasive grids. The first large scale docking experiment ran on the EGEE grid production service from 11 July 2005 to 19 August 2005 against targets relevant to research on malaria and saw over 41 million compounds docked for the equivalent of 80 years of CPU time. Up to 1,700 computers were simultaneously used in 15 countries around the world. Issues related to the deployment and the monitoring of the in silico docking experiment as well as experience with grid operation and services are reported in the paper. The main problem encountered for such a large scale deployment was the grid infrastructure stability. Although the overall success rate was above 80%, a lot of monitoring and supervision was still required at the application level to resubmit the jobs that failed. But the experiment demonstrated how grid infrastructures have a tremendous capacity to mobilize very large CPU resources for well targeted goals during a significant period of time. This success leads to a second computing challenge targeting Avian Flu neuraminidase N1