Quantum retrodiction: foundations and controversies

TL;DR

This paper explores the foundations of quantum retrodiction, clarifying its basis in Bayesian probability and addressing common controversies, demonstrating its universal applicability within quantum theory.

Contribution

It establishes the foundational principles of quantum retrodiction and clarifies its connection to Bayesian methods, resolving misunderstandings in the literature.

Findings

Quantum retrodiction is universally valid within quantum theory.

It is fundamentally linked to Bayesian probability.

The paper clarifies misconceptions about retrodiction in quantum physics.

Abstract

Prediction is the making of statements, usually probabilistic, about future events based on current information. Retrodiction is the making of statements about past events based on current information. We present the foundations of quantum retrodiction and highlight its intimate connection with the Bayesian interpretation of probability. The close link with Bayesian methods enables us to explore controversies and misunderstandings about retrodiction that have appeared in the literature. To be clear, quantum retrodiction is universally applicable and draws its validity directly from conventional predictive quantum theory coupled with Bayes' theorem.