Delayed Twin Observables Are They a Fundamental Concept in Quantum Mechanics?

TL;DR

This paper explores the concept of delayed twin observables in quantum mechanics, extending their definition beyond composite systems and demonstrating their relevance in quantum preparation, measurement, and resolving experimental puzzles.

Contribution

It generalizes the notion of twin observables to delayed twins in non-composite systems and links them to practical quantum processes and experiments.

Findings

Delayed twin observables can be defined in non-composite systems.

They provide insights into quantum state preparation and measurement.

Exact measurement can be understood as an opposite-subsystem delayed twin.

Abstract

Opposite-subsystem twin events and twin observables, studied previously in the context of distant correlations, are first generalized to pure states of not-necessarily-composite systems, and afterwards they are further generalized to delayed twins that are due to unitary evolution of the quantum system. The versatile aspects of delayed twin observables are studied in terms of necessary and sufficient conditions to make possible various applications. Three of these are sketched: Preparation of some quantum experiments, easy solution of a puzzle in an important Scully et al. real experiment, and, finally, it is shown that exact measurement in quantum mechanics is an example of opposite-subsystem delayed twins in bipartite pure states.