Which-Way Measurement and Momentum Kicks

TL;DR

This paper demonstrates that the loss of interference in which-way experiments can be interpreted either as entanglement or as random momentum kicks, showing these views are equivalent and extending the analysis to multiple slits.

Contribution

It introduces a dual interpretation framework for which-way measurement effects, unifying entanglement and momentum kick perspectives across multiple slit experiments.

Findings

Interference loss can be viewed as entanglement or momentum kicks.

Equivalent descriptions hold for two-slit, three-slit, and n-slit experiments.

No need for local versus nonlocal kick distinctions.

Abstract

Two-slit interference experiment with a which-way detector has been a topic of intense debate. Scientific community is divided on the question whether the particle receives a momentum kick because of the process of which-way measurement. It is shown here that the same experiment can be viewed in two different ways, depending on which basis of the which-way detector states one chooses to look at. In one view, the loss of interference arises due to the entanglement of the two paths of the particle with two orthogonal states of the which-way detector. In another view, the loss of interference can be interpreted as arising from random momentum kicks of magnitude $h/2d$ received by the particle, $d$ being the slit separation. The same scenario is shown to hold for a three-slit interference experiment. The random momentum kicks for the three-slit case are of two kinds, of magnitude $\pm h/3d$. The analysis is also generalized to the case of n-slit interference. The two alternate views are described by the same quantum state, and hence are completely equivalent. The concept of "local" versus "nonlocal" kicks, much discussed in the literature, is not needed here.