Continuous-Variable Quantum Teleportation with a Conventional Laser (Rev. Ver.)

Abstract

We give a description of balanced homodyne detection (BHD) using a conventional laser as a local oscillator (LO), where the laser field outside the cavity is a mixed state whose phase is completely unknown. Our description is based on the standard interpretation of the quantum theory for measurement, and accords with the experimental result in the squeezed state generation scheme. We apply our description of BHD to continuous-variable quantum teleportation (CVQT) with a conventional laser to analyze the CVQT experiment [A. Furusawa et al., Science 282, 706 (1998)], whose validity has been questioned on the ground of intrinsic phase indeterminacy of the laser field [T. Rudolph and B.C. Sanders, Phys. Rev. Lett. 87, 077903 (2001)]. We show that CVQT with a laser is valid only if the unknown phase of the laser field is shared among sender's LOs, the EPR state, and receiver's LO. The CVQT experiment is considered valid with the aid of an optical path other than the EPR channel and a classical channel, directly linking between a sender and a receiver. We also propose a method to probabilistically generate a strongly phase-correlated quantum state via continuous measurement of independent lasers, which is applicable to realizing CVQT without the additional optical path.

5 pages, 2 figures. This is a revised version of quant-ph/0301045. I have not replaced that original version with this revised one so that readers can easily verify priority of ideas first presented in the original version in every arXiv mirror site. I changed the part referring to the papers by van Enk and Fuchs, emphasizing a fundamental difference in claims between their papers and mine

References in corpus (4)

• Postselected versus nonpostselected quantum teleportation using parametric down-conversion
• Fidelity and information in the quantum teleportation of continuous variables
• The Quantum State of an Ideal Propagating Laser Field
• Requirement of optical coherence for continuous-variable quantum teleportation

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• Relativistic quantum information theory and quantum reference frames
• Teleportation of Continuous Quantum Variables: A New Approach