# Nondemolition observation of a free quantum particle.

@article{Belavkin1992NondemolitionOO, title={Nondemolition observation of a free quantum particle.}, author={Belavkin and Staszewski}, journal={Physical review. A, Atomic, molecular, and optical physics}, year={1992}, volume={45 3}, pages={ 1347-1356 } }

A stochastic model of a continuous nondemolition observation of a free quantum Brownian motion is presented. The nonlinear stochastic wave equation describing the posterior dynamics of the observed quantum system is solved in a Gaussian case for a free particle of mass m > 0. It is shown that the dispersion of the wave packet does not increase to in
nity like for the free unobserved particle but tends to the
nite limit 1 = (~=2 m) where is the accuracy coe¢ cient of an indirect nondemolition…

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