2,058 research outputs found
Generation of Narrow-Band Polarization-Entangled Photon Pairs for Atomic Quantum Memories
We report an experimental realization of a narrow-band polarization-entangled
photon source with a linewidth of 9.6 MHz through cavity-enhanced spontaneous
parametric down-conversion. This linewidth is comparable to the typical
linewidth of atomic ensemble based quantum memories. Single-mode output is
realized by setting a reasonable cavity length difference between different
polarizations, using of temperature controlled etalons and actively stabilizing
the cavity. The entangled property is characterized with quantum state
tomography, giving a fidelity of 94% between our state and a maximally
entangled state. The coherence length is directly measured to be 32 m through
two-photon interference.Comment: 4 pages, 4 figure
Experimental Quantum Teleportation and Multi-Photon Entanglement via Interfering Narrowband Photon Sources
In this letter, we report a realization of synchronization-free quantum
teleportation and narrowband three-photon entanglement through interfering
narrowband photon sources. Since both the single-photon and the entangled
photon pair utilized are completely autonomous, it removes the requirement of
high demanding synchronization technique in long-distance quantum communication
with pulsed spontaneous parametric down-conversion sources. The frequency
linewidth of the three-photon entanglement realized is on the order of several
MHz, which matches the requirement of atomic ensemble based quantum memories.
Such a narrowband multi-photon source will have applications in some advanced
quantum communication protocols and linear optical quantum computation
Deterministic and Efficient Quantum Cryptography Based on Bell's Theorem
We propose a novel double-entanglement-based quantum cryptography protocol
that is both efficient and deterministic. The proposal uses photon pairs with
entanglement both in polarization and in time degrees of freedom; each
measurement in which both of the two communicating parties register a photon
can establish one and only one perfect correlation and thus deterministically
create a key bit. Eavesdropping can be detected by violation of local realism.
A variation of the protocol shows a higher security, similarly to the six-state
protocol, under individual attacks. Our scheme allows a robust implementation
under current technology.Comment: 4 pages, 1 figure; published version with a note adde
Optical Nondestructive Controlled-NOT Gate without Using Entangled Photons
We present and experimentally demonstrate a novel optical nondestructive
controlled-NOT gate without using entangled ancilla. With much fewer
measurements compared with quantum process tomography, we get a good estimation
of the gate fidelity. The result shows a great improvement compared with
previous experiments. Moreover, we also show that quantum parallelism is
achieved in our gate and the performance of the gate can not be reproduced by
local operations and classical communications.Comment: 5 pages, 3 figures, Slight changes have been made, Journal-ref adde
CCA-secure unidirectional proxy re-encryption in the adaptive corruption model without random oracles
Proxy re-encryption (PRE), introduced by Blaze, Bleumer and Strauss in Eurocrypt\u2798, allows a semi-trusted proxy to convert a ciphertext originally intended for Alice into an encryption of the same message intended for Bob. PRE has recently drawn great interest, and many interesting PRE schemes have been proposed. However, up to now, it is still an important question to come up with a chosen-ciphertext secure unidirectional PRE in the adaptive corruption model. To address this problem, we propose a new unidirectional PRE scheme, and prove its chosen-ciphertext security in the adaptive corruption model without random oracles. Compared with the best known unidirectional PRE scheme proposed by Libert and Vergnaud in PKC\u2708, our schemes enjoys the advantages of both higher efficiency and stronger security
Radiative transitions in charmonium from twisted mass lattice QCD
We present a study for charmonium radiative transitions:
, and
using twisted mass lattice QCD gauge
configurations. The single-quark vector form factors for and
are also determined. The simulation is performed at a lattice
spacing of fm and the lattice size is . After
extrapolation of lattice data at nonzero to 0, we compare our results
with previous quenched lattice results and the available experimental values.Comment: typeset with revtex, 15 pages, 11 figures, 4 table
Isospin Effect on the Process of Multifragmentation and Dissipation at Intermediate Energy Heavy Ion Collisions
In the simulation of intermediate energy heavy ion collisions by using the
isospin dependent quantum molecular dynamics, the isospin effect on the process
of multifragmentation and dissipation has been studied. It is found that the
multiplicity of intermediate mass fragments for the neutron-poor
colliding system is always larger than that for the neutron-rich system, while
the quadrupole of single particle momentum distribution for the
neutron-poor colliding system is smaller than that of the neutron-rich system
for all projectile-target combinations studied at the beam energies from about
50MeV/nucleon to 150MeV/nucleon. Since depends strongly on isospin
dependence of in-medium nucleon-nucleon cross section and weakly on symmetry
potential at the above beam energies, it may serve as a good probe to extract
the information on the in-medium nucleon-nucleon cross section. The correlation
between the multiplicity of intermediate mass fragments and the total
numer of charged particles has the behavior similar to , which
can be used as a complementary probe to the in-medium nucleon-nucleon cross
section.Comment: 18 pages, 9 figure
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