How the instant collapse of a spatially-extended quantum state is consistent with relativity of simultaneity

TL;DR

This paper demonstrates that quantum mechanics' instantaneous wave function collapse is consistent with relativity of simultaneity, using the Born postulate to show invariance and addressing instant disentanglement.

Contribution

It provides a novel proof that quantum collapse invariance follows from the Born postulate, ensuring consistency with relativity without relying on operator properties.

Findings

Quantum collapse invariance follows from the Born postulate.

Quantum mechanics remains consistent with relativity for instant disentanglement.

Mathematical structure of quantum mechanics eliminates contradictions with relativity.

Abstract

A thought experiment is considered on observation of instantaneous collapse of an extended wave packet. According to relativity of simultaneity, such a collapse being instantaneous in some reference frame must be a lasting process in other frames. But according to quantum mechanics, collapse is instantaneous in any frame. Mathematical structure of quantum mechanics eliminates any contradictions between these two apparently conflicting statements. Here the invariance of quantum-mechanical collapse is shown to follow directly from the Born postulate, without any use of mathematical properties of quantum operators. The consistency of quantum mechanics with Relativity is also shown for instant disentanglement of a composite system.