Quantum homogenization for continuous variables: Realization with linear optical elements

Journal Article · Sun Dec 01 04:00:00 EST 2002 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.66.062307· OSTI ID:20632415

Nagaj, Daniel ^[1]; Stelmachovic, Peter ^[2]; Buzek, Vladimir ^[2]; Kim, Myungshik ^[3]

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1. Department of Theoretical Physics, FMPI, Comenius University, 842 28 Bratislava (Slovakia)
2. Research Center for Quantum Information, Slovak Academy of Sciences, Dubravska cesta 9, 84228 Bratislava (Slovakia)
3. School of Mathematics and Physics, The Queen's University, Belfast BT7 1NN (United Kingdom)

Recently Ziman et al. [Phys. Rev. A 65, 042105 (2002)] have introduced a concept of a universal quantum homogenizer which is a quantum machine that takes as input a given (system) qubit initially in an arbitrary state {rho} and a set of N reservoir qubits initially prepared in the state {xi}. The homogenizer realizes, in the limit sense, the transformation such that at the output each qubit is in an arbitrarily small neighborhood of the state {xi} irrespective of the initial states of the system and the reservoir qubits. In this paper we generalize the concept of quantum homogenization for qudits, that is, for d-dimensional quantum systems. We prove that the partial-swap operation induces a contractive map with the fixed point which is the original state of the reservoir. We propose an optical realization of the quantum homogenization for Gaussian states. We prove that an incoming state of a photon field is homogenized in an array of beam splitters. Using Simon's criterion, we study entanglement between outgoing beams from beam splitters. We derive an inseparability condition for a pair of output beams as a function of the degree of squeezing in input beams.

• OSTI ID: 20632415
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 6 Vol. 66; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

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BINDING ENERGY
CONVERGENCE
ENERGY LEVELS
PHOTONS
QUANTUM MECHANICS
TRANSFORMATIONS