Quantum entanglement and Bell nonlocality in top-quark pair production at a photon linear collider

TL;DR

This paper explores how a photon linear collider can be used to observe quantum entanglement and Bell nonlocality in top-quark pair production, leveraging controllable photon polarization to probe fundamental quantum phenomena.

Contribution

It demonstrates that a photon linear collider is an ideal platform for studying quantum entanglement and Bell nonlocality in top-quark pairs through detailed spin density matrix analysis.

Findings

Photon polarization control enhances entanglement observability.

Photon linear collider effectively probes quantum nonlocality.

Spin density matrix construction reveals entanglement across phase space.

Abstract

A photon linear collider, the two-photon collision mode of an $e^+e^-$ linear collider, uses high-energy laser photons backscattered off the incoming electrons and positrons. The colliding-photon polarization is fully controllable through the polarizations of the initial electron and positron beams and laser photons. We investigate the impact of colliding-photon polarization on the observability of quantum entanglement in top-quark pair production at a photon linear collider. Constructing the spin density matrix of the $t\bar{t}$ two-qubit system from the helicity amplitudes, we demonstrate that a photon linear collider is an ideal machine to probe quantum entanglement and Bell nonlocality across the broad phase space of the process.