Broadening the scope of weak quantum measurements II: Past and future measurement effects within a double Mach-Zehnder-interferometer setting

TL;DR

This paper investigates the temporal effects of weak and strong measurements in a double Mach-Zehnder interferometer, revealing how interference and which-path information can coexist and be recovered, challenging traditional interpretations of quantum measurement.

Contribution

It extends previous work by analyzing temporal peculiarities of weak measurements in a complex interferometer setup, including single-particle scenarios and implications for quantum interpretations.

Findings

Weak measurements do not prevent consecutive interference effects.

Which-path information can be recovered after weak measurements using strong measurements.

The results support the Two-State-Vector Formalism in quantum mechanics.

Abstract

Following earlier applications of weak measurement to new cases (Part I), we proceed to explore its temporal peculiarities. We analyze an idealized experiment in which weak which-path measurements do not prevent consecutive weak interference effects, and then again the which-path information is recovered by strong measurements. We also show how the same effect can be obtained even by all these measurements being carried out on a single particle. The simplified setting enables critically assessing competing interpretations of the results. The most natural one is that of the Two-State-Vector Formalism, according to which the quantum "two-state" between an earlier and a later measurement is equally determined by both of them.