Numerical investigation of the logarithmic Schr\"odinger model of quantum decoherence

Abstract

A logarithmic Schr\"odinger equation with time-dependent coupling to the non-linearity is presented as a model of collisional decoherence of the wavefunction of a quantum particle in position-space. The particular mathematical form of the logarithmic Schr\"odinger equation has been shown to follow from conditional wave theory, but the validity of the logarithmic Schr\"odinger equation has not yet been investigated numerically for general initial conditions. Using an operator-splitting approach, we solve the non-linear equation of motion for the wavefunction numerically and compare it it to the solution of the standard Joos-Zeh master equation for the density matrix. We find good agreement for the time-dependent behaviour of the ensemble widths between the two approaches, but note curious `zero-pinning' behaviour of the logarithmic Schr\"odinger equation, whereby the zeros of the wavefunction are not erased by continued propagation. By examining the derivation of the logarithmic Schr\"odinger equation from conditional wave theory, we indicate possible avenues of resolution to this zero-pinning problem.