1,068 research outputs found
Generating Hermite polynomial excited squeezed states by means of conditional measurements on a beam splitter
A scheme for conditional generating a Hermite polynomial excited squeezed
vacuum states (HESVS) is proposed. Injecting a two-mode squeezed vacuum state
(TMSVS) into a beam splitter (BS) and counting the photons in one of the output
channels, the conditional state in the other output channel is just a HESVS. To
exhibit a number of nonclassical effects and non-Guassianity, we mainly
investigate the photon number distribution, sub-Poissonian distribution,
quadrature component distribution, and quasi-probability distribution of the
HPESVS. We find that its nonclassicality closely relates to the control
parameter of the BS, the squeezed parameter of the TMSVS, and the photon number
of conditional measurement. These further demonstrate that performing the
conditional measurement on a BS is an effective approach to generate
non-Guassian state.Comment: 8 pages, 8 figures. arXiv admin note: text overlap with
arXiv:quant-ph/9703039 by other author
Asymptotic behavior of a hydrodynamic system in the nematic liquid crystal flows
In this paper we study the long time behavior of the classical
solutions to a hydrodynamical system modeling the flow of nematic
liquid crystals. This system consists of a coupled system of
Navier--Stokes equations and kinematic transport equations for the
molecular orientations. By using a suitable Lojasiewicz--Simon
type inequality, we prove the convergence of global solutions to
single steady states as time tends to infinity. Moreover, we provide
estimates for the convergence rate
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
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