Abstract:
The path integration method is used to describe the evolution of a quantum system subject to continuous (in time) measurement. It is shown that nonselective continuous measurement leads to a continuous increase in the degree of mixing of states. A scheme is developed
for calculating a family of “partial” evolution operators that describe the dynamics of the system with allowance for the back reaction of the instrument, and a generalized unitarity condition for them is formulated. The general results are then applied to the case
of spectral measurements of a harmonic oscillator. The nature of the
mixing which arises as a result of such measurements is analyzed.
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