Addressing Local Realism through Bell Tests at Colliders

TL;DR

This paper explores the feasibility of Bell tests in high-energy collider experiments, demonstrating that while local realism cannot be tested directly, quantum correlations remain observable and informative in such settings.

Contribution

It introduces a framework for Bell tests at colliders where outcomes are inferred indirectly, showing local realism tests are infeasible but quantum correlations can still be studied.

Findings

Bell tests are not possible with indirect measurements at colliders.

Quantum correlations can be measured and analyzed despite the inability to test local realism.

The approach provides new insights into quantum phenomena in high-energy physics environments.

Abstract

One of the most notable aspects of quantum systems is that their components can exhibit correlations much stronger than those allowed by classical physics. Two examples of quantum correlations are quantum entanglement and Bell nonlocality, but generally there is a hierarchy of many types of quantum correlations. Among these correlations, Bell nonlocality holds a special place because it plays a dual role in distinguishing theories where local realism is a valid description. A Bell test, which is a test of local realism, typically needs to be augmented with assumptions to address possible loopholes in the experimental setup. In this work, we study Bell tests in experiments in which the detector reports the correct outcome with a specified probability. This mirrors the situation at high-energy colliders, where particle spins are not measured directly but inferred from the angular distributions of their decay products. We show that, in this setup, a test of local realism is not possible. Quantum correlations, however, are still present, measurable, and informative in high-energy colliders.