Past of a particle inside an interferometer: the two-state vector approach

TL;DR

This paper defends the two-state vector approach to understanding a quantum particle’s past within an interferometer, demonstrating its consistency with quantum mechanics and its utility in analyzing interference experiments.

Contribution

It clarifies and supports the two-state vector approach against criticisms, showing its effectiveness and consistency in various interference scenarios.

Findings

The approach explains all considered examples effectively.

It remains consistent with standard quantum mechanics.

It is a useful tool for interference experiment analysis.

Abstract

Hashmi et al. [J. Phys. A 49, 345302 (2016)] claimed that the approach to the past of a quantum particle introduced by Vaidman [Phys. Rev. A 87, 052104 (2013)] has difficulties in certain examples and that it even can be refuted. Here I reply to their criticism showing that the approach provides a good explanation of all examples they considered. It is fully consistent with standard quantum mechanics and provides a useful tool for analyzing interference experiments.