Entanglement and nonlocality of a single relativistic particle

TL;DR

This paper demonstrates that a single relativistic spin-1/2 particle can exhibit entanglement and violate Bell's inequality across different inertial frames, highlighting the fundamental nature of single-particle entanglement in relativistic quantum mechanics.

Contribution

It shows that single-particle entanglement persists under relativistic boosts and can lead to Bell inequality violations, extending nonlocality concepts to relativistic single particles.

Findings

Entanglement survives at relativistic speeds up to the speed of light.

Boosted observers see violations of Bell's inequality with a single particle.

Implications for quantum information processing with relativistic particles.

Abstract

Recent work has argued that the concepts of entanglement and nonlocality must be taken seriously even in systems consisting of only a single particle. These treatments, however, are nonrelativistic and, if single particle entanglement is fundamental, it should also persist in a relativistic description. Here we consider a spin-1/2 particle in a superposition of two different velocities as viewed by an observer in a different relativistically-boosted inertial frame. We show that the entanglement survives right up to the speed of light and that the boosted observer would see single-particle violations of Bell's inequality. We also discuss how quantum gates could be implemented in this way and the possible implications for quantum information processing.