Correlation between measured and unmeasured quantities in quantum mechanics, locality, and the legitimacy of counterfactual reasoning

TL;DR

This paper introduces a correlation measure for measured and unmeasured quantities in quantum mechanics, examines locality implications, extends to no-signalling frameworks, and questions counterfactual reasoning's validity.

Contribution

It presents a new correlation measure, applies it to locality tests, extends analysis to no-signalling boxes, and critically discusses counterfactual reasoning in quantum theory.

Findings

Correlation measure relates measured and unmeasured quantities

Locality implications for Bell/CHSH setups analyzed

Counterfactual reasoning in quantum mechanics questioned

Abstract

A correlation measure relating to measured and unmeasured local quantities in quantum mechanics is introduced, and is then applied to assess the locality implications for Bell/CHSH and similar set-ups. This leads to some interesting results, and the scheme is extended to the generalized no-signalling boxes framework. Some questions are raised about the use of counterfactual reasoning in quantum mechanics.