3,071 research outputs found
Passive scheme with a photon-number-resolving detector for monitoring the untrusted source in a plug-and-play quantum-key-distribution system
A passive scheme with a beam splitter and a photon-number-resolving (PNR)
detector is proposed to verify the photon statistics of an untrusted source in
a plug-and-play quantum-key-distribution system by applying a three-intensity
decoy-state protocol. The practical issues due to statistical fluctuation and
detection noise are analyzed. The simulation results show that the scheme can
work efficiently when the total number of optical pulses sent from Alice to Bob
is above 10^8, and the dark count rate of the PNR detector is below 0.5
counts/pulse, which is realizable with current techniques. Furthermore, we
propose a practical realization of the PNR detector with a variable optical
attenuator combined with a threshold detector.Comment: 8 pages, 6 figure
A Possibility of Search for New Physics at LHCb
It is interesting to search for new physics beyond the standard model at
LHCb. We suggest that weak decays of doubly charmed baryon such as
to charmless final states would be a possible
signal for new physics. In this work, we consider two models, i.e. the
unparticle and as examples to study such possibilities. We also discuss
the cases for which have not been observed yet, but
one can expect to find them when LHCb begins running. Our numerical results
show that these two models cannot result in sufficiently large decay widths,
therefore if such modes are observed at LHCb, there must be a new physics other
than the unparticle or models.Comment: 7 pages, 3 figures, 1 table. More references and discussion adde
On the Poisson Approximation to Photon Distribution for Faint Lasers
It is proved, that for a certain kind of input distribution, the strongly
binomially attenuated photon number distribution can well be approximated by a
Poisson distribution. This explains why we can adopt poissonian distribution as
the photon number statistics for faint lasers. The error of such an
approximation is quantitatively estimated. Numerical tests are carried out,
which coincide with our theoretical estimations. This work lays a sound
mathematical foundation for the well-known intuitive idea which has been widely
used in quantum cryptography
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