408 research outputs found
Autonomous Robust Skill Generation Using Reinforcement Learning with Plant Variation
This paper discusses an autonomous space robot for a truss structure assembly using some reinforcement learning. It is difficult for a space robot to complete contact tasks within a real environment, for example, a peg-in-hole task, because of error between the real environment and the controller model. In order to solve problems, we propose an autonomous space robot able to obtain proficient and robust skills by overcoming error to complete a task. The proposed approach develops skills by reinforcement learning that considers plant variation, that is, modeling error. Numerical simulations and experiments show the proposed method is useful in real environments
Increased fitness of a key appendicularian zooplankton species under warmer, acidified seawater conditions
Ocean warming and acidification (OA) may alter the fitness of species in marine pelagic ecosystems through community effects or direct physiological impacts. We used the zooplanktonic appendicularian, Oikopleura dioica, to assess temperature and pH effects at mesocosm and microcosm scales. In mesocosms, both OA and warming positively impacted O. dioica abundance over successive generations. In microcosms, the positive impact of OA, was observed to result from increased fecundity. In contrast, increased pH, observed for example during phytoplankton blooms, reduced fecundity. Oocyte fertility and juvenile development were equivalent under all pH conditions, indicating that the positive effect of lower pH on O. dioica abundance was principally due to increased egg number. This effect was influenced by food quantity and quality, supporting possible improved digestion and assimilation at lowered pH. Higher temperature resulted in more rapid growth, faster maturation and earlier reproduction. Thus, increased temperature and reduced pH had significant positive impacts on O. dioica fitness through increased fecundity and shortened generation time, suggesting that predicted future ocean conditions may favour this zooplankton species. © 2018 Bouquet et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
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
Dispersive properties of quasi-phase-matched optical parametric amplifiers
The dispersive properties of non-degenerate optical parametric amplification
in quasi-phase-matched (QPM) nonlinear quadratic crystals with an arbitrary
grating profile are theoretically investigated in the no-pump-depletion limit.
The spectral group delay curve of the amplifier is shown to be univocally
determined by its spectral power gain curve through a Hilbert transform. Such a
constraint has important implications on the propagation of spectrally-narrow
optical pulses through the amplifier. In particular, it is shown that anomalous
transit times, corresponding to superluminal or even negative group velocities,
are possible near local minima of the spectral gain curve. A possible
experimental observation of such effects using a QPM Lithium-Niobate crystal is
suggested.Comment: submitted for publicatio
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
Controlling a superconducting nanowire single-photon detector using tailored bright illumination
We experimentally demonstrate that a superconducting nanowire single-photon
detector is deterministically controllable by bright illumination. We found
that bright light can temporarily make a large fraction of the nanowire length
normally-conductive, can extend deadtime after a normal photon detection, and
can cause a hotspot formation during the deadtime with a highly nonlinear
sensitivity. In result, although based on different physics, the
superconducting detector turns out to be controllable by virtually the same
techniques as avalanche photodiode detectors. As demonstrated earlier, when
such detectors are used in a quantum key distribution system, this allows an
eavesdropper to launch a detector control attack to capture the full secret key
without being revealed by to many errors in the key.Comment: Expanded discussions, updated references. 9 pages, 8 figure
Detector decoy quantum key distribution
Photon number resolving detectors can enhance the performance of many
practical quantum cryptographic setups. In this paper, we employ a simple
method to estimate the statistics provided by such a photon number resolving
detector using only a threshold detector together with a variable attenuator.
This idea is similar in spirit to that of the decoy state technique, and is
specially suited for those scenarios where only a few parameters of the photon
number statistics of the incoming signals have to be estimated. As an
illustration of the potential applicability of the method in quantum
communication protocols, we use it to prove security of an entanglement based
quantum key distribution scheme with an untrusted source without the need of a
squash model and by solely using this extra idea. In this sense, this detector
decoy method can be seen as a different conceptual approach to adapt a single
photon security proof to its physical, full optical implementation. We show
that in this scenario the legitimate users can now even discard the double
click events from the raw key data without compromising the security of the
scheme, and we present simulations on the performance of the BB84 and the
6-state quantum key distribution protocols.Comment: 27 pages, 7 figure
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
Qualitative study of system-level factors related to genomic implementation
PURPOSE:
Research on genomic medicine integration has focused on applications at the individual level, with less attention paid to implementation within clinical settings. Therefore, we conducted a qualitative study using the Consolidated Framework for Implementation Research (CFIR) to identify system-level factors that played a role in implementation of genomic medicine within Implementing GeNomics In PracTicE (IGNITE) Network projects.
METHODS:
Up to four study personnel, including principal investigators and study coordinators from each of six IGNITE projects, were interviewed using a semistructured interview guide that asked interviewees to describe study site(s), progress at each site, and factors facilitating or impeding project implementation. Interviews were coded following CFIR inner-setting constructs.
RESULTS:
Key barriers included (1) limitations in integrating genomic data and clinical decision support tools into electronic health records, (2) physician reluctance toward genomic research participation and clinical implementation due to a limited evidence base, (3) inadequate reimbursement for genomic medicine, (4) communication among and between investigators and clinicians, and (5) lack of clinical and leadership engagement.
CONCLUSION:
Implementation of genomic medicine is hindered by several system-level barriers to both research and practice. Addressing these barriers may serve as important facilitators for studying and implementing genomics in practice
- …