Measuring Quantum Discord at the LHC

TL;DR

This paper proposes methods to measure quantum discord in top anti-top quark pairs at the LHC, providing analytical formulas and demonstrating feasible precision levels for collider experiments, thus advancing quantum information studies in particle physics.

Contribution

It introduces analytical formulas for quantum discord in the top anti-top system and demonstrates its potential measurability at the LHC with high precision.

Findings

Quantum discord can be analytically computed for the t-tbar system.

High-luminosity LHC can measure discord with about 5% precision.

Current datasets allow 1-2% precision measurement of discord.

Abstract

There has been an increasing interest in exploring quantities associated with quantum information at colliders. We perform a detailed analysis describing how to measure the quantum discord in the top anti-top quantum state at the Large Hadron Collider (LHC). While for pure states, quantum discord, entanglement, and Bell nonlocality all probe the same correlations, for mixed states they probe different aspects of quantum correlations. The quantum discord, in particular, is interesting because it aims to encapsulate all correlations between systems that cannot have a classical origin. We employ two complementary approaches for the study of the top anti-top system, namely the decay method and the kinematic method. We highlight subtleties associated with measuring discord for reconstructed quantum states at colliders. Usually quantum discord is difficult to compute due to an extremization that must be performed. We show, however, that for the $t\bar{t}$ system this extremization can be performed analytically and we provide closed-form formulas for the quantum discord. We demonstrate that at the high luminosity LHC, discord is projected to be measurable with a precision of approximately 5% using the decay method and sub-percent levels using the kinematic method. Even with current LHC datasets, discord can be measured with 1-2% precision with the kinematic method. By systematically investigating quantum discord for the first time through a detailed collider analysis, this work expands the toolkit for quantum information studies in particle physics and lays the groundwork for deeper insights into the quantum properties in high-energy collisions.