Does a measurement really collapse the wave function?

TL;DR

This paper questions the traditional wave function collapse postulate, proposing that multiple branches of a quantum wave-function can coexist and interfere, challenging the idea that measurement causes the wave function to reduce to a single outcome.

Contribution

It introduces an experiment demonstrating that detectors cause decoherence but do not eliminate other branches of the wave-function, suggesting a revision of the collapse concept.

Findings

Detectors cause decoherence without collapsing the wave function.

Multiple branches of the wave-function can coexist and produce interference.

The collapse postulate may not be necessary to explain measurement outcomes.

Abstract

A single-particle multi-branched wave-function is studied. Usual which-path tests show that if the detector placed on one branch clicks, the detectors on the other branches remain silent. By the collapse postulate, after this click, the state of the particle is reduced to a single branch, the branch on which the detector clicked. The present article challenges the collapse postulate, claiming that when one branch of the wave-function produces a click in a detector, the other branches don't disappear. They can't produce clicks in detectors, but they are still there. An experiment different from which-path test is proposed, which shows that detectors are responsible for strongly decohering the wave-function, but not for making parts of it disappear. Moreover, one of the branches supposed to disappear may produce an interference pattern with a wave-packet of another particle.