Generation of entangled coherent states via cross-phase-modulation in a double electromagnetically induced transparency regime

Journal Article · Sat Feb 01 00:00:00 EST 2003 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.67.023811· OSTI ID:20633768

Paternostro, M; Kim, M S; Ham, B S ^[1]

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1. School of Mathematics and Physics, The Queen's University, Belfast BT7 1NN (United Kingdom)

The generation of an entangled coherent state is one of the most important ingredients of quantum information processing using coherent states. Recently, numerous schemes to achieve this task have been proposed. In order to generate travelling-wave entangled coherent states, cross-phase-modulation, optimized by optical Kerr effect enhancement in a dense medium in an electromagnetically induced transparency (EIT) regime, seems to be very promising. In this scenario, we propose a fully quantized model of a double-EIT scheme recently proposed [D. Petrosyan and G. Kurizki, Phys. Rev. A 65, 33 833 (2002)]: the quantization step is performed adopting a fully Hamiltonian approach. This allows us to write effective equations of motion for two interacting quantum fields of light that show how the dynamics of one field depends on the photon-number operator of the other. The preparation of a Schroedinger cat state, which is a superposition of two distinct coherent states, is briefly exposed. This is based on nonlinear interaction via double EIT of two light fields (initially prepared in coherent states) and on a detection step performed using a 50:50 beam splitter and two photodetectors. In order to show the entanglement of an entangled coherent state, we suggest to measure the joint quadrature variance of the field. We show that the entangled coherent states satisfy the sufficient condition for entanglement based on quadrature variance measurement. We also show how robust our scheme is against a low detection efficiency of homodyne detectors.

• OSTI ID: 20633768
• Journal Information: Physical Review. A, Vol. 67, Issue 2; Other Information: DOI: 10.1103/PhysRevA.67.023811; (c) 2003 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ANNIHILATION OPERATORS
BEAM SPLITTING
CORRELATIONS
DETECTION
EFFICIENCY
EIGENSTATES
EQUATIONS OF MOTION
HAMILTONIANS
INFORMATION THEORY
KERR EFFECT
MODULATION
NONLINEAR PROBLEMS
OPACITY
PHOTODETECTORS
PHOTONS
QUADRATURES
QUANTIZATION
QUANTUM MECHANICS
TRAVELLING WAVES
VISIBLE RADIATION