Searching Quantum Entanglement in $p\ p\to Z\ Z$ process

TL;DR

This paper demonstrates that quantum entanglement can be detected in the $pp o ZZ$ process at the LHC using quantum state tomography and simulated data, suggesting feasible experimental tests of entanglement in high-energy physics.

Contribution

It introduces a method to reconstruct the spin density matrix of the $ZZ$ system at colliders and shows entanglement detection is possible with current and future LHC data.

Findings

Entanglement can be probed at 2σ level with LHC Run 2+3 data.

Higher luminosity increases detection significance up to 3.75σ.

Quantum state tomography is effective for analyzing collider-produced entangled states.

Abstract

Recent studies have shown that observing entangled particle states at a particle collider like Large Hadron Collider (LHC) and testing violation of Bell inequality in them can open up new research area for high energy physics study. We examine the presence of quantum entanglement in the $pp\to ZZ\to 4\ell$ process at leading order. We apply generally recognized method, quantum state tomography, to reconstruct spin density matrix of the joint $ZZ$ system, through which all the relevant observables can be obtained. The angular distribution of the final leptons are obtained from simulated events using Monte-Carlo program, which is used to reconstruct spin density matrix. Non-zero value of the lower bound of the concurrence is measured with simulated data. The numerical analysis shows that with the luminosity corresponding to LHC Run 2+3, entanglement can be probed at $2 \sigma$ level and up to 3.75$\sigma$ level for High-Luminosity LHC data ($3 \rm{ab}^{-1}$), revealing the possibility of finding quantum entanglement in real collider experiment.