1,926 research outputs found
Continuous-variable multipartite unlockable bound entangled Gaussian states
Continuous-variable (CV) multipartite unlockable bound-entangled states is
investigated in this paper. Comparing with the qubit multipartite unlockable
bound-entangled states, CV multipartite unlockable bound-entangled states
present the new and different properties. CV multipartite unlockable
bound-entangled states may serve as a useful quantum resource for new
multiparty communication schemes. The experimental protocol for generating CV
unlockable bound-entangled states is proposed with a setup that is at present
accessible.Comment: 6 pages, 4 figure
Characterization of Collective Gaussian Attacks and Security of Coherent-State Quantum Cryptography
We provide a simple description of the most general collective Gaussian
attack in continuous-variable quantum cryptography. In the scenario of such
general attacks, we analyze the asymptotic secret-key rates which are
achievable with coherent states, joint measurements of the quadratures and
one-way classical communication.Comment: 4 pages, 1 figure + 1 Table, REVteX. More descriptive titl
Optical implementation of continuous-variable quantum cloning machines
We propose an optical implementation of the Gaussian continuous-variable
quantum cloning machines. We construct a symmetric N -> M cloner which
optimally clones coherent states and we also provide an explicit design of an
asymmetric 1 -> 2 cloning machine. All proposed cloning devices can be built
from just a single non-degenerate optical parametric amplifier and several beam
splitters.Comment: 4 pages, 3 figures, REVTe
Universal cloning of continuous quantum variables
The cloning of quantum variables with continuous spectra is analyzed. A
universal - or Gaussian - quantum cloning machine is exhibited that copies
equally well the states of two conjugate variables such as position and
momentum. It also duplicates all coherent states with a fidelity of 2/3. More
generally, the copies are shown to obey a no-cloning Heisenberg-like
uncertainty relation.Comment: 4 pages, RevTex. Minor revisions, added explicit cloning
transformation, added reference
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