Coupling classical and quantum variables using continuous quantum measurement theory

May, 1997
12 pages
Published in:
  • Phys.Rev.Lett. 81 (1998) 2846-2849
e-Print:
Report number:
  • IMPERIAL-TP-96-97-46,
  • IC-96-97-46,
  • Imperial College preprint 96-97/46

Citations per year

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Abstract:
We propose a system of equations to describe the interaction of a quasiclassical variable XX with a set of quantum variables xx that goes beyond the usual mean field approximation. The idea is to regard the quantum system as continuously and imprecisely measured by the classical system. The effective equations of motion for the classical system therefore consist of treating the quantum variable xx as a stochastic c-number \x (t) the probability distibution for which is given by the theory of continuous quantum measurements. The resulting theory is similar to the usual mean field equations (in which xx is replaced by its quantum expectation value) but with two differences: a noise term, and more importantly, the state of the quantum subsystem evolves according to the stochastic non-linear Schrodinger equation of a continuously measured system. In the case in which the quantum system starts out in a superposition of well-separated localized states, the classical system goes into a statistical mixture of trajectories, one trajectory for each individual localized state.
Note:
  • 11 pages, plain Tex (with revised settings for \vsize and \voffset to accommodate US paper sizes)