0512188v1

related topics
{measurement, state, measurements}
{operator, operators, space}
{observables, space, algebra}
{state, states, coherent}
{group, space, representation}
{energy, gaussian, time}
{equation, function, exp}
{field, particle, equation}
{time, systems, information}
{states, state, optimal}
{time, decoherence, evolution}

Nondemolition Principle of Quantum Measurement Theory

V. P. Belavkin

abstract: We give an explicit axiomatic formulation of the quantum measurement theory which is free of the projection postulate. It is based on the generalized nondemolition principle applicable also to the unsharp, continuous-spectrum and continuous-in-time observations. The "collapsed state-vector" after the "objectification" is simply treated as a random vector of the a posteriori state given by the quantum filtering, i.e., the conditioning of the a priori induced state on the corresponding reduced algebra. The nonlinear phenomenological equation of "continuous spontaneous localization" has been derived from the Schroedinger equation as a case of the quantum filtering equation for the diffusive nondemolition measurement. The quantum theory of measurement and filtering suggests also another type of the stochastic equation for the dynamical theory of continuous reduction, corresponding to the counting nondemolition measurement, which is more relevant for the quantum experiments.

oai_identifier:
oai:arXiv.org:quant-ph/0512188
categories:
quant-ph
comments:
23 pages. See also related papers at http://www.maths.nott.ac.uk/personal/vpb/research/mes_fou.html and http://www.maths.nott.ac.uk/personal/vpb/research/cau_idy.html
arxiv_id:
quant-ph/0512188
journal_ref:
Foundations of Physics, 24 (1994) No 5, 685--714
created:
2005-12-21

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