112 research outputs found
Experimental quantum key distribution with source flaws
Decoy-state quantum key distribution (QKD) is a standard technique in current
quantum cryptographic implementations. Unfortunately, existing experiments have
two important drawbacks: the state preparation is assumed to be perfect without
errors and the employed security proofs do not fully consider the finite-key
effects for general attacks. These two drawbacks mean that existing experiments
are not guaranteed to be secure in practice. Here, we perform an experiment
that for the first time shows secure QKD with imperfect state preparations over
long distances and achieves rigorous finite-key security bounds for decoy-state
QKD against coherent attacks in the universally composable framework. We
quantify the source flaws experimentally and demonstrate a QKD implementation
that is tolerant to channel loss despite the source flaws. Our implementation
considers more real-world problems than most previous experiments and our
theory can be applied to general QKD systems. These features constitute a step
towards secure QKD with imperfect devices.Comment: 12 pages, 4 figures, updated experiment and theor
Performance enhancement of permeable asphalt mixtures with recycled aggregate for concrete pavement application
The incorporation of recycled concrete aggregate (RCA) in permeable asphalt mixtures (PAMs) is an efficient method of utilizing construction demolished waste. It not only conforms to the trend of building sponge cities, but also alleviates the problem of overexploitation of natural aggregate resources. As the performance of PAM containing recycled aggregate is not comparable to natural aggregate, modification treatments and the addition of hybrid fibers are adopted as two enhancement methods to improve the performance of PAM with RAC in this study. It is found that replacing natural aggregate with recycled aggregate increases the optimum asphalt content (OAC) but decreases the residual stability. The OAC is increased by 45% when the RCA ratio is 100%, whereas applying silicone resin can give a 16.2% decrease in the OAC. Enhancing RCA with silicone resin can increase the water stability to be comparable with natural aggregate. Moreover, with modification treatment using calcium hydroxide solution, the mechanical strength of PAM is enhanced to even higher than that of natural coarse aggregate mixture alone. Improvements in both mechanical strength and water stability are also achieved by strengthening recycled aggregate with cement slurry, although the performance is less effective than using silicone resin. With the increase in the content of RCA, the permeability coefficients of PAM first decrease and then exhibit an increasing trend. The results indicate that the PAM with RCA and modification treatments can perform satisfactorily as a pavement material in practice. Applying probable modification, PAM incorporating RCA meets the criteria for use in concrete pavement applications
No Exchange of Picornaviruses in Vietnam between Humans and Animals in a High-Risk Cohort with Close Contact despite High Prevalence and Diversity
Hospital-based and community-based ‘high-risk cohort’ studies investigating humans at risk of zoonotic infection due to occupational or residential exposure to animals were conducted in Vietnam, with diverse viruses identified from faecal samples collected from humans, domestic and wild animals. In this study, we focus on the positive-sense RNA virus family Picornaviridae, investigating the prevalence, diversity, and potential for cross-species transmission. Through metagenomic sequencing, we found picornavirus contigs in 23% of samples, belonging to 15 picornavirus genera. Prevalence was highest in bats (67%) while diversity was highest in rats (nine genera). In addition, 22% of the contigs were derived from novel viruses: Twelve phylogenetically distinct clusters were observed in rats of which seven belong to novel species or types in the genera Hunnivirus, Parechovirus, Cardiovirus, Mosavirus and Mupivirus; four distinct clusters were found in bats, belonging to one novel parechovirus species and one related to an unclassified picornavirus. There was no evidence for zoonotic transmission in our data. Our study provides an improved knowledge of the diversity and prevalence of picornaviruses, including a variety of novel picornaviruses in rats and bats. We highlight the importance of monitoring the human–animal interface for possible spill-over events
Analysis of air quality changes and causes in the Liaoning region from 2017 to 2022
Using the air quality monitoring data from the Department of Ecology and Environment of Liaoning Province for the period from 2017 to 2022, the temporal and spatial changes in the concentrations of various air pollutants in the Liaoning region for the periods from 2017 to 2019 and 2020 to 2022 were analyzed by using the Evaluation on the meteorological condition index of PM2.5 pollution (EMI) and the ArcGIS Kriging Interpolation Method, and the contributions of pollution reduction to the changes in the air quality of the Liaoning region were assessed. The results show that after the implementation of emission reduction measures, the quality of the atmospheric environment in the Liaoning region has significantly improved, and the mean concentrations of PM2.5, PM10, SO2, NO2, CO and O3 are all reduced by a certain magnitude in the period 2020 to 2022 compared with the period 2017 to 2019; Based on the EMI index calculation, the average EMI index in Liaoning during the period 2020 to 2022 is about 1.7% lower than the average value of the region during the period 2017 to 2019, and the atmospheric dispersion conditions are relatively good; From the perspective of daily changes in pollutant concentrations, the trend of PM2.5 and PM10 concentrations changed from double peaks and single valleys to single peaks and single valleys, and there were no significant changes in the types of valleys for CO, SO2, NO2, and O3, whereas the peaks of O3 concentrations during the daytime were basically the same as in previous years, and the concentrations during the nighttime were slightly higher than in previous years. Classification by topographic areas revealed that the mean pollutant concentration for the period from 2017 to 2019 was more significant than the mean value for the period from 2020 to 2022, except for O3, where the air quality in the mountainous areas of Liaodong and Liaoxi was better than that of the Liaohe Plain, and regional classification by coastal and inland, where the air quality in the coastal areas was better than that of the inland areas
Paramagnons and high-temperature superconductivity in a model family of cuprates
Cuprate superconductors have the highest critical temperatures (Tc) at ambient pressure, yet
a consensus on the superconducting mechanism remains to be established. Finding an
empirical parameter that limits the highest reachable Tc can provide crucial insight into this
outstanding problem. Here, in the first two Ruddlesden-Popper members of the model Hg-
family of cuprates, which are chemically nearly identical and have the highest Tc among all
cuprate families, we use inelastic photon scattering to reveal that the energy of magnetic
fluctuations may play such a role. In particular, we observe the single-paramagnon spectra to
be nearly identical between the two compounds, apart from an energy scale difference of
~30% which matches their difference in Tc. The empirical correlation between paramagnon
energy and maximal Tc is further found to extend to other cuprate families with relatively high
Tc’s, hinting at a fundamental connection between them
High-speed measurement-device-independent quantum key distribution with integrated silicon photonics
Measurement-device-independent quantum key distribution (MDI-QKD) removes all
detector side channels and enables secure QKD with an untrusted relay. It is
suitable for building a star-type quantum access network, where the complicated
and expensive measurement devices are placed in the central untrusted relay and
each user requires only a low-cost transmitter, such as an integrated photonic
chip. Here, we experimentally demonstrate a 1.25 GHz silicon photonic
chip-based MDI-QKD system using polarization encoding. The photonic chip
transmitters integrate the necessary encoding components for a standard QKD
source. We implement random modulations of polarization states and decoy
intensities, and demonstrate a finite-key secret rate of 31 bps over 36 dB
channel loss (or 180 km standard fiber). This key rate is higher than
state-of-the-art MDI-QKD experiments. The results show that silicon photonic
chip-based MDI-QKD, benefiting from miniaturization, low-cost manufacture and
compatibility with CMOS microelectronics, is a promising solution for future
quantum secure networks.Comment: 30 pages, 12 figure
Experimental quantum key distribution secure against malicious devices
The fabrication of quantum key distribution (QKD) systems typically involves
several parties, thus providing Eve with multiple opportunities to meddle with
the devices. As a consequence, conventional hardware and/or software hacking
attacks pose natural threats to the security of practical QKD. Fortunately, if
the number of corrupted devices is limited, the security can be restored by
using redundant apparatuses. Here, we report on the demonstration of a secure
QKD setup with optical devices and classical post-processing units possibly
controlled by an eavesdropper. We implement a 1.25 GHz chip-based
measurement-device-independent QKD system secure against malicious devices on
\emph{both} the measurement and the users' sides. The secret key rate reaches
137 bps over a 24 dB channel loss. Our setup, benefiting from high clock rate,
miniaturized transmitters and a cost-effective structure, provides a promising
solution for widespread applications requiring uncompromising communication
security.Comment: 28 pages, 5 figures, 4 table
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