Fidelity criterion for quantum-domain transmission and storage of coherent states beyond the unit-gain constraint.
We generalize the experimental success criterion for quantum teleportation (memory) in continuous-variable quantum systems to be suitable for a non-unit-gain condition by considering attenuation (amplification) of the coherent-state amplitude. The new criterion can be used for a nonideal quantum memory and long distance quantum communication as well as quantum devices with amplification process. It is also shown that the framework to measure the average fidelity is capable of detecting all Gaussian channels in the quantum domain.
Namiki
Ryo
R
CREST Research Team for Photonic Quantum Information, Division of Materials Physics, Department of Materials Engineering Science, Graduate school of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. namiki@qi.mp.es.osaka-u.ac.jp
Koashi
Masato
M
Imoto
Nobuyuki
N