Top Quarks & Quantum Entanglement in Collisions

Researchers at Anhui University, led by Duo-Duo Chen, have presented a comprehensive investigation of quantum correlations within top quark-antiquark pairs produced through quantum chromodynamics (QCD). The analysis employs a suite of quantum information theoretic measures, notably quantum mutual information and relative entropy of coherence, to characterise the relationships between these particles’ kinematic properties and quantum states. This work demonstrates a significant connection between the production of gluons, fundamental force-carrying particles, and the strength of quantum correlations. This potentially offers valuable insights into the underlying quantum structure of QCD and providing a novel avenue for exploring physics beyond the Standard Model.

Gluon production directly correlates with quantum coherence in top quark pairs

A quantifiable relationship between gluon production and quantum correlations in top quark-antiquark pairs has been established. The research reveals that the maximum value of the left-hand side of a specific intrinsic relation increases proportionally with the probability of gluon production, denoted as Wgg. This finding allows for a detailed investigation utilising not only quantum mutual information (QMI), relative entropy of coherence (REC), and complete complementarity relations, but also a newly derived intrinsic relation. This extends beyond the limitations of previous studies which often focused on single measures of quantum entanglement. The significance of this lies in the fact that gluons mediate the strong force, and understanding their influence on the quantum state of top quarks is crucial for a complete understanding of QCD.

Prior investigations into quantum correlations within heavy quark systems often relied on quantifying entanglement using a limited set of measures, providing an incomplete picture of the overall quantumness. This study, however, offers a more holistic characterisation of quantum behaviour within the framework of quantum chromodynamics, encompassing a wider range of initial-state mixtures. The top quark, with a mass of approximately 173.1 ±0.6 GeV, presents a unique opportunity for such studies due to its exceptionally short lifetime, on the order of 10−25 seconds. This incredibly rapid decay preserves the spin polarization of the quark, meaning the initial quantum state is largely unaffected by decay processes, enabling a detailed examination of the quantum correlations present at the moment of its creation. Larger values of quantum mutual information (QMI) and relative entropy of coherence (REC) signify stronger total correlations and a greater degree of quantumness, respectively. QMI is typically bounded between 0 and 2 log2 d, while REC ranges from 0 to log2 d, where ‘d’ represents the dimension of the single-particle Hilbert space. Complete complementarity relations, a core concept in quantum information theory, were employed to link coherence, predictability, and correlations, providing a more comprehensive understanding of the distribution of quantum information within the system. These relations highlight the inherent trade-offs between different aspects of quantum information, offering a nuanced perspective on the observed correlations.

Top quark correlations illuminate strong force dynamics and potential new physics

There is a growing emphasis within the particle physics community on quantifying the subtle quantum connections between particles, aiming for a more profound understanding of the fundamental forces governing the universe. Quantifying these relationships within top quark pairs is particularly valuable, as it provides a new and powerful set of tools for analysing the vast amounts of data generated by high-energy particle colliders such as the Large Hadron Collider. This methodology not only allows for refinement of existing theoretical models of QCD, but also opens the possibility of detecting deviations from the Standard Model, potentially hinting at the existence of new particles or interactions. Mapping quantum links within top quark-antiquark pairs, created via quantum chromodynamics, utilises measures like QMI and REC to quantify the shared information and predictability between the particles. The resulting data can be compared with theoretical predictions, allowing physicists to test the validity of current models and search for discrepancies that might indicate new physics.

The inherent complexity of modelling quantum chromodynamics (QCD) presents a significant challenge in establishing a definitive link between these quantum correlations and undiscovered physics. QCD is a non-perturbative theory, meaning that exact solutions are often impossible to obtain, and approximations must be used. This introduces uncertainties into the theoretical predictions, making it difficult to isolate the effects of new physics. However, by carefully analysing the quantum correlations and comparing them with increasingly precise theoretical calculations, researchers hope to overcome these challenges. The study of top quark pairs is particularly sensitive to new physics due to the large mass of the top quark, which enhances the effects of virtual particles that might contribute to deviations from the Standard Model. Furthermore, the precise measurement of top quark properties, including its spin correlations, can provide stringent tests of the Standard Model’s predictions.

Future research will focus on extending this methodology to other particle systems, such as Higgs boson pairs and diboson systems, to determine whether similar quantum correlations are present. Exploring the implications of these findings for precision tests of the Standard Model, including measurements of the top quark’s decay properties and its interactions with other particles, is also a key priority. Ultimately, a deeper understanding of quantum correlations in heavy quark systems could unlock new insights into the fundamental nature of the strong force and pave the way for discoveries beyond the Standard Model.

The research demonstrated quantum correlations within pairs of top quarks created through quantum chromodynamics. These correlations, quantified using measures such as quantum mutual information, offer a means to test the accuracy of current theoretical models describing the strong force. Findings indicate the level of quantum correlation changes with the probability of gluon mixing, providing insight into the quantum nature of QCD. The authors intend to expand this methodology to other particle systems, like Higgs boson pairs, to investigate whether similar correlations exist.