70 research outputs found
Quantum Logical Gates with Linear Quadripartite Cluster States of Continuous Variables
The concrete schemes to realize three types of basic quantum logical gates
using linear quadripartite cluster states of optical continuous variables are
proposed. The influences of noises and finite squeezing on the computation
precision are analyzed in terms of the fidelity of propagated quantum
information through the continuous variable cluster states. The proposed
schemes provide direct references for the design of experimental systems of
one-way quantum computer based on the cluster entanglement of amplitude and
phase quadratures of light.Comment: accepted for publication by PR
Quantum Communication Network Utilizing Quadripartite Entangled States of Optical Field
We propose two types of quantum dense coding communication networks with
optical continuous variables, in which a quadripartite entangled state of the
optical field with totally three-party correlations of quadrature amplitudes is
utilized. In the networks, the exchange of information between any two
participants can be manipulated by one or two of the remaining participants.
The channel capacities for a variety of communication protocols are numerically
calculated. Due to the fact that the quadripartite entangled states applied in
the communication systems have been successfully prepared already in the
laboratory, the proposed schemes are experimentally accessible at present
Cascaded Entanglement Enhancement
We present a cascaded system consisting of three non-degenerate optical
parametric amplifiers (NOPAs) for the generation and the enhancement of quantum
entanglement of continuous variables. The entanglement of optical fields
produced by the first NOPA is successively enhanced by the second and the third
NOPAs from -5.3 to -8.1 below the quantum noise limit. The dependence
of the enhanced entanglement on the physical parameters of the NOPAs and the
reachable entanglement limitation for a given cascaded NOPA system are
calculated. The calculation results are in good agreement with the experimental
measurements.Comment: 5 pages, 4 figure
Nonlocal Nondegenerate Optical Parametric Amplifier Based on Genuine Multipartite Entanglement
We propose a new scheme for realizing nonlocal nondegenerate optical
parametric amplifier by means of genuine four-mode entanglement. The
nondegenerate optical parametric amplifier is regarded as a unitary
transformation from two input fields to two outputs. Two inputs and two outputs
are located at the remote stations respectively. Employing off-line four-mode
entanglement, homodyne detection, classical communication and local
displacement, the nonlocal nondegenerate optical parametric amplifier can be
achieved. This scheme can be implemented with a setup that is experimentally
accessible at present.Comment: 3 pages, 1 figures, submitted to Phys. Rev.
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