670 research outputs found
Near-Complete Teleportation of a Superposed Coherent State
The four Bell-type entangled coherent states, |\alpha>|-\alpha> \pm |-\alpha>
|\alpha> and |\alpha>|\alpha> \pm |-\alpha> |-\alpha>, can be discriminated
with a high probability using only linear optical means, as long as |\alpha| is
not too small. Based on this observation, we propose a simple scheme to almost
completely teleport a superposed coherent state. The nonunitary transformation,
that is required to complete the teleportation, can be achieved by embedding
the receiver's field state in a larger Hilbert space consisting of the field
and a single atom and performing a unitary transformation on this Hilbert
space.Comment: 4 pages,3 figures, Two columns, LaTex2
Robustness of multiparty nonlocality to local decoherence
We investigate the robustness of multiparty nonlocality under local
decoherence, acting independently and equally on each subsystems. To be
specific, we consider an N-qubit GHZ state under depolarization, dephasing, or
dissipation channel, and tested the nonlocality by violation of Mermin-Klyshko
inequality, which is one of Bell's inequalities for multi-qubit systems. The
results show that the robustness of nonlocality increases with the number of
qubits, and that the nonlocality of an N-qubit GHZ state with even N is
extremely persistent against dephasing.Comment: 5 pages, 4 figure
Adaptive Pilot Signaling in the Uplink of OFDM-Based Wireless Systems
Orthogonal frequency division multiplexing (OFDM)
has been considered as one of key transmission technologies for
high-speed wireless communication systems. For channel-adaptive
transmission of OFDM signal, base stations transmit a common
pilot signal in the downlink, but mobile stations transmit
individual pilot signal in the uplink. As a consequence, the uplink
may suffer from poorer channel estimation accuracy than the
downlink. This problem can be alleviated by increasing the pilot
signal density. But this reduces the time and frequency resources
for the data transmission, deteriorating the actual transmission
throughput. In this paper, we propose an adaptive pilot signaling
scheme that adjusts the pilot density in response to the change of
channel characteristics. Simulation results show that the proposed
scheme can remarkably reduce the pilot overhead without
performance degradation, compared to conventional schemes
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