Comment on 'Quantum measurement and decoherence'

Journal Article · Sun Aug 01 04:00:00 EDT 2004 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.70.026101· OSTI ID:20645978

Gobert, Dominique; Delft, Jan von; Ambegaokar, Vinay ^[1]

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1. Sektion Physik und CeNS, Ludwigs-Maximilians-Universitaet, Theresienstr. 37, 80333 Muenchen (Germany)

Ford, Lewis, and O'Connell [Phys. Rev. A 64, 032101 (2001)] have recently discussed a thought experiment in which a Brownian particle is subjected to a double-slit measurement . Analyzing the decay of the emerging interference pattern, they derive a decoherence rate that is much faster than previous results and even persists in the limit of vanishing dissipation. This result is based on the definition of a certain attenuation factor, which they analyze for short times. In this note, we point out that this attenuation factor captures the physics of decoherence only for times larger than a certain time t{sub mix}, which is the time it takes until the two emerging wave packets begin to overlap. Therefore, the strategy of Ford et al. of extracting the decoherence time from the regime t<t{sub mix} is in our opinion not meaningful. If one analyzes the attenuation factor for t>t{sub mix}, one recovers familiar behavior for the decoherence time; in particular, no decoherence is seen in the absence of dissipation. We confirm the latter conclusion by calculating the off-diagonal elements of the reduced density matrix.

• OSTI ID: 20645978
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 2 Vol. 70; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ATTENUATION
BROWNIAN MOVEMENT
DECAY
DENSITY MATRIX
INTERFERENCE
PARTICLES
QUANTUM MECHANICS
WAVE PACKETS