1,446 research outputs found
Universal Thermoelectric Effect of Dirac Fermions in Graphene
We numerically study the thermoelectric transports of Dirac fermions in
graphene in the presence of a strong magnetic field and disorder. We find that
the thermoelectric transport coefficients demonstrate universal behavior
depending on the ratio between the temperature and the width of the
disorder-broadened Landau levels(LLs). The transverse thermoelectric
conductivity reaches a universal quantum value at the center of
each LL in the high temperature regime, and it has a linear temperature
dependence at low temperatures. The calculated Nernst signal has a peak at the
central LL with heights of the order of , and changes sign near other
LLs, while the thermopower has an opposite behavior, in good agreement with
experimental data. The validity of the generalized Mott relation between the
thermoelectric and electrical transport coefficients is verified in a wide
range of temperatures.Comment: 4 pages, 4 figures, published versio
Effect of source tampering in the security of quantum cryptography
The security of source has become an increasingly important issue in quantum
cryptography. Based on the framework of measurement-device-independent
quantum-key-distribution (MDI-QKD), the source becomes the only region
exploitable by a potential eavesdropper (Eve). Phase randomization is a
cornerstone assumption in most discrete-variable (DV-) quantum communication
protocols (e.g., QKD, quantum coin tossing, weak coherent state blind quantum
computing, and so on), and the violation of such an assumption is thus fatal to
the security of those protocols. In this paper, we show a simple quantum
hacking strategy, with commercial and homemade pulsed lasers, by Eve that
allows her to actively tamper with the source and violate such an assumption,
without leaving a trace afterwards. Furthermore, our attack may also be valid
for continuous-variable (CV-) QKD, which is another main class of QKD protocol,
since, excepting the phase random assumption, other parameters (e.g.,
intensity) could also be changed, which directly determine the security of
CV-QKD.Comment: 9 pages, 6 figure
2,2′-[(4,6-Dinitro-1,3-phenylene)dioxy]diacetic acid hemihydrate
The skeletons of both independent molecules of the carboxylic acid hemihydrate, C10H8N2O10·0.5H2O, are approximately planar [maximum deviations 0.642 (3) and 0.468 (1) Å]. The deviations arise from the twisting of the nitro groups with respect to the aromatic rings [dihedral angles = 3.24 (2) and 27.01 (1), and 7.87 (1) and 16.37 (2)° in the two molecules]. The crystal structure features intermolecular O—H⋯O hydrogen bonds, which the link the dicarboxylic acid and water molecules into a supramolecular layer network
- …