A microscopic model of wave-function dephasing and decoherence in the double-slit experiment

TL;DR

This paper presents a microscopic, non-Markovian model of wave-function dephasing and decoherence in the double-slit experiment, revealing non-exponential short-time behavior and connecting it to long-term exponential decay.

Contribution

It introduces a simple, calculable non-Markovian model that challenges the usual exponential assumption for short-time wave-function collapse.

Findings

Short-time behavior is non-exponential.

Connects quadratic-in-time transition probability to exponential decay.

Provides a calculable example without Markovian approximation.

Abstract

The act of measurement on a quantum state is supposed to "collapse" the state into one of several eigenstates of the operator corresponding to the observable being measured. This measurement process is sometimes described as outside standard quantum-mechanical evolution and not calculable from Schr\"odinger's equation. There are two general approaches to the study of wave-function collapse: one called the "consistent" or "decoherent" histories approach and the other, the "environmental decoherence" approach, which studies the effect of the environment upon the quantum system, to explain wave-function collapse. In the "environmental decoherence" approach, one usually studies a Markovian-approximated Master equation to study the time-evolution of reduced density matrix and obtains the long-term dependence of the off-diagonal elements of this matrix. We do not make a Markovian assumption and study a particularly simple and calculable example. We find, the short-time behavior of a collapsing system, at least the one considered in this paper, is not exponential, which is a new result (the long-term behavior is, of course, still exponential). This allows one to connect the Fermi-golden rule quadratic-in-time behavior of a transition probability to the exponential long-time behavior of a collapsing wave-function.