5,544 research outputs found
Terahertz Atmospheric Windows for High Angular Resolution Terahertz Astronomy from Dome A
Atmospheric transmission from Dome A, Antarctica, presents new possibilities
in the field of terahertz astronomy, where space telescopes have been the only
observational tools until now. Using atmospheric transmission measurements from
Dome A with a Fourier transform spectrometer, transmission spectra and
long-term stabilities have been analyzed at 1.461 THz, 3.393 THz, 5.786 THz and
7.1 THz, which show that important atmospheric windows for terahertz astronomy
open for a reasonable length of time in the winter season. With large aperture
terahertz telescopes and interferometers at Dome A, high angular resolution
terahertz observations are foreseen of atomic fine-structure lines from ionized
gas and a water ice feature from protoplanetary disks.Comment: 6 pages, 3 figures, to appear in Advances in Polar Scienc
F-wave heavy-light meson spectroscopy in QCD sum rules and heavy quark effective theory
We study the F-wave c_bar s heavy meson doublets (2+,3+) and (3+,4+). They
have large orbital excitations L=3, and may be good challenges (tests) for
theoretical studies. To study them we use the method of QCD sum rule in the
framework of heavy quark effective theory. Their masses are predicted to be
m_{(2+,3+)} = (3.45 \pm 0.25, 3.50 \pm 0.26) GeV and m_{(3+,4+)} = (3.20 \pm
0.22, 3.26 \pm 0.23) GeV, with mass splittings Delta m_{(2+,3+)} = m_{3+} -
m_{2+} = 0.046 \pm 0.030 GeV and Delta m_{(3+,4+)} = 0.053 \pm 0.044 GeV,
respectively. We note that this is a pioneering work and these results are
provisional.Comment: 10 pages, 8 figures, 3 tables, accepted by PR
Passive faraday mirror attack in practical two-way quantum key distribution system
The faraday mirror (FM) plays a very important role in maintaining the
stability of two way plug-and-play quantum key distribution (QKD) system.
However, the practical FM is imperfect, which will not only introduce
additional quantum bit error rate (QBER) but also leave a loophole for Eve to
spy the secret key. In this paper, we propose a passive faraday mirror attack
in two way QKD system based on the imperfection of FM. Our analysis shows that,
if the FM is imperfect, the dimension of Hilbert space spanned by the four
states sent by Alice is three instead of two. Thus Eve can distinguish these
states with a set of POVM operators belonging to three dimension space, which
will reduce the QBER induced by her attack. Furthermore, a relationship between
the degree of the imperfection of FM and the transmittance of the practical QKD
system is obtained. The results show that, the probability that Eve loads her
attack successfully depends on the degree of the imperfection of FM rapidly,
but the QBER induced by Eve's attack changes with the degree of the
imperfection of FM slightly
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