Decoherence and determinism in a one-dimensional cloud-chamber model

TL;DR

This paper investigates how a one-dimensional quantum model can explain the emergence of linear tracks in cloud chambers, exploring the roles of decoherence, determinism, and atom positions in quantum measurement.

Contribution

It extends a one-dimensional spin model to analyze the measurement process and the influence of atom positions on detection outcomes, providing both time-dependent and time-independent perspectives.

Findings

Wave packet evolution can be deterministic in the model.

Spin-excitation probabilities are highly sensitive to model parameters.

Preliminary results support the idea that atom positions influence measurement results.

Abstract

The hypothesis by Sparenberg et al. (2013) that the particular linear tracks appearing in the measurement of a spherically-emitting radioactive source in a cloud chamber are determined by the (random) positions of atoms or molecules inside the chamber is further explored in the framework of a recently established one-dimensional model by Carlone et al. (2015). In this model, meshes of localized spins 1/2 play the role of the cloud-chamber atoms and the spherical wave is replaced by a linear superposition of two wave packets moving from the origin to the left and to the right, evolving deterministically according to the Schr\"odinger equation. We first revisit these results using a time-dependent approach, where the wave packets impinge on a symmetric two-sided detector. We discuss the evolution of the wave function in the configuration space and stress the interest of a non-symmetric detector in a quantum-measurement perspective. Next we use a time-independent approach to study the scattering of a plane wave on a single-sided detector. Preliminary results are obtained, analytically for the single-spin case and numerically for up to 8 spins. They show that the spin-excitation probabilities are sometimes very sensitive to the parameters of the model, which corroborates the idea that the measurement result could be determined by the atom positions. The possible origin of decoherence and entropy increase in future models is finally discussed.