1,914 research outputs found
Multiparty Quantum Secret Sharing
Based on a quantum secure direct communication (QSDC) protocol [Phys. Rev.
A69(04)052319], we propose a -threshold scheme of multiparty quantum
secret sharing of classical messages (QSSCM) using only single photons. We take
advantage of this multiparty QSSCM scheme to establish a scheme of multiparty
secret sharing of quantum information (SSQI), in which only all quantum
information receivers collaborate can the original qubit be reconstructed. A
general idea is also proposed for constructing multiparty SSQI schemes from any
QSSCM scheme
Multiparty Quantum Secret Sharing Based on Entanglement Swapping
A multiparty quantum secret sharing (QSS) protocol is proposed by using
swapping quantum entanglement of Bell states. The secret messages are imposed
on Bell states by local unitary operations. The secret messages are split into
several parts and each part is distributed to a party so that no action of a
subset of all the parties but their entire cooperation is able to read out the
secret messages. In addition, the dense coding is used in this protocol to
achieve a high efficiency. The security of the present multiparty QSS against
eavesdropping has been analyzed and confirmed even in a noisy quantum channel.Comment: 5 page
Phase Reversal Diffraction in incoherent light
Phase reversal occurs in the propagation of an electromagnetic wave in a
negatively refracting medium or a phase-conjugate interface. Here we report the
experimental observation of phase reversal diffraction without the above
devices. Our experimental results and theoretical analysis demonstrate that
phase reversal diffraction can be formed through the first-order field
correlation of chaotic light. The experimental realization is similar to phase
reversal behavior in negatively refracting media.Comment: 8 pages, 5 figure
On product-one sequences over dihedral groups
Let be a finite group. A sequence over means a finite sequence of
terms from , where repetition is allowed and the order is disregarded. A
product-one sequence is a sequence whose elements can be ordered such that
their product equals the identity element of the group. The set of all
product-one sequences over (with concatenation of sequences as the
operation) is a finitely generated C-monoid. Product-one sequences over
dihedral groups have a variety of extremal properties. This article provides a
detailed investigation, with methods from arithmetic combinatorics, of the
arithmetic of the monoid of product-one sequences over dihedral groups.Comment: to appear in Journal of Algebra and its Application
Neutron Scattering Measurements of Spatially Anisotropic Magnetic Exchange Interactions in Semiconducting K0.85Fe1.54Se2 (TN=280 K)
We use neutron scattering to study the spin excitations associated with the
stripe antiferromagnetic (AFM) order in semiconducting
KFeSe (= K). We show that the spin wave spectra
can be accurately described by an effective Heisenberg Hamiltonian with highly
anisotropic in-plane couplings at = K. At high temperature (=
K) above , short range magnetic correlation with anisotropic correlation
lengths are observed. Our results suggest that, despite the dramatic difference
in the Fermi surface topology, the in-plane anisotropic magnetic couplings are
a fundamental property of the iron based compounds; this implies that their
antiferromagnetism may originate from local strong correlation effects rather
than weak coupling Fermi surface nesting.Comment: 5 pages, 4 figure
Enhanced Orbital Degeneracy in Momentum Space for LaOFeAs
The Fermi surfaces (FS) of LaOFeAs (in =0 plane) consist of two
hole-type circles around point, which do not touch each other, and two
electron-type co-centered ellipses around M point, which are degenerate along
the M-X line. By first-principles calculations, here we show that additional
degeneracy exists for the two electron-type FS, and the crucial role of
F-doping and pressure is to enhance this orbital degeneracy. It is suggested
that the inter-orbital fluctuation is the key point to understand the
unconventional superconductivity in these materials.Comment: 4 pages, 5 figure
Square patterns in Rayleigh-Benard convection with rotation about a vertical axis
We present experimental results for Rayleigh-Benard convection with rotation
about a vertical axis at dimensionless rotation rates in the range 0 to 250 and
upto 20% above the onset. Critical Rayleigh numbers and wavenumbers agree with
predictions of linear stability analysis. For rotation rates greater than 70
and close to onset, the patterns are cellular with local four-fold coordination
and differ from the theoretically expected Kuppers-Lortz unstable state. Stable
as well as intermittent defect-free square lattices exist over certain
parameter ranges. Over other ranges defects dynamically disrupt the lattice but
cellular flow and local four-fold coordination is maintained.Comment: ReVTeX, 4 pages, 7 eps figures include
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