Gaussian cloning of coherent states with known phases
Abstract
The fidelity for cloning coherent states is improved over that provided by optimal Gaussian and nonGaussian cloners for the subset of coherent states that are prepared with known phases. Gaussian quantum cloning duplicates all coherent states with an optimal fidelity of 2/3. NonGaussian cloners give optimal singleclone fidelity for a symmetric 1to2 cloner of 0.6826. Coherent states that have known phases can be cloned with a fidelity of 4/5. The latter is realized by a combination of two beam splitters and a fourwave mixer operated in the nonlinear regime, all of which are realized by interaction Hamiltonians that are quadratic in the photon operators. Therefore, the known Gaussian devices for cloning coherent states are extended when cloning coherent states with known phases by considering a nonbalanced beam splitter at the input side of the amplifier.
 Authors:
 Department of Physics and Physical Oceanography, University of North Carolina at Wilmington, Wilmington, North Carolina 28403 (United States)
 Publication Date:
 OSTI Identifier:
 20787177
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physical Review. A; Journal Volume: 73; Journal Issue: 4; Other Information: DOI: 10.1103/PhysRevA.73.045801; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 74 ATOMIC AND MOLECULAR PHYSICS; AMPLIFIERS; ANNIHILATION OPERATORS; BEAM SPLITTING; CLONING; EIGENSTATES; ENERGY LEVELS; HAMILTONIANS; NONLINEAR PROBLEMS; OPTICS; PHOTONS; QUANTUM COMPUTERS
Citation Formats
Alexanian, Moorad. Gaussian cloning of coherent states with known phases. United States: N. p., 2006.
Web. doi:10.1103/PHYSREVA.73.0.
Alexanian, Moorad. Gaussian cloning of coherent states with known phases. United States. doi:10.1103/PHYSREVA.73.0.
Alexanian, Moorad. Sat .
"Gaussian cloning of coherent states with known phases". United States.
doi:10.1103/PHYSREVA.73.0.
@article{osti_20787177,
title = {Gaussian cloning of coherent states with known phases},
author = {Alexanian, Moorad},
abstractNote = {The fidelity for cloning coherent states is improved over that provided by optimal Gaussian and nonGaussian cloners for the subset of coherent states that are prepared with known phases. Gaussian quantum cloning duplicates all coherent states with an optimal fidelity of 2/3. NonGaussian cloners give optimal singleclone fidelity for a symmetric 1to2 cloner of 0.6826. Coherent states that have known phases can be cloned with a fidelity of 4/5. The latter is realized by a combination of two beam splitters and a fourwave mixer operated in the nonlinear regime, all of which are realized by interaction Hamiltonians that are quadratic in the photon operators. Therefore, the known Gaussian devices for cloning coherent states are extended when cloning coherent states with known phases by considering a nonbalanced beam splitter at the input side of the amplifier.},
doi = {10.1103/PHYSREVA.73.0},
journal = {Physical Review. A},
number = 4,
volume = 73,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}

We investigate the economical Gaussian cloning of coherent states with the known phase, which produces M copies from N input replica and can be implemented with degenerate parametric amplifiers and beam splitters.The achievable fidelity of single copy is given by 2M{radical}(N)/[{radical}(N)(M1)+{radical}((1+N)(M{sup 2}+N))], which is bigger than the optimal fidelity of the universal Gaussian cloning. The cloning machine presented here works without ancillary optical modes and can be regarded as the continuous variable generalization of the economical cloning machine for qudits.

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