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Physical Review Letters

Monte Carlo Method for Evaluating the Quantum Real Time Propagator

Shesheng Zhang, Eli Pollak

Published Nov 6, 2003• 75 citations
Publisher

Abstract

A new exact representation of the quantum propagator is derived in terms of semiclassical initial value representations. The resulting expression may be expanded in a series, of which the leading order term is the semiclassical one. Motion of a Gaussian wave packet on a symmetric double well potential is used to demonstrate numerical convergence of the series and the ability to compute each element in the series using Monte Carlo methods.

DOI
10.1103/physrevlett.91.190201

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The recently derived exact representation of the quantum propagator in terms of semiclassical initial value representations (SCIVR) is used to optimize the width parameter in the SCIVR. Minimization of the expectation value of the correction operator related to the SCIVR leads to improved convergence of the representation. A test on a model one-dimensional double-well potential demonstrates that this optimization can give essentially exact results using only the first two terms in the SCIVR expansion of the exact propagator.
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A new algorithm for modeling quantum dynamics of wave packets in a semiclassical limit was formulated and justified. The algorithm is valid in the case of two-particle systems and in the case of a single particle in any arbitrary central potential. The profile of the wave packet depending on the time for a single wave packet evolving in a one-dimensional (1D) Morse potential was obtained by direct computer simulations using the new algorithm. The results were compared with the calculation which was previously performed using the Initial Value Representation (IVR) method.
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