The measurement of top-quark spin correlations provides a key tool for probing its interactions with high precision. Owing to its extremely short lifetime ($τ\sim 10^{-25}$ s), the top quark preserves its spin polarization information, making the $t\bar{t}$ system an ideal framework for investigating quantum correlations in high-energy physics. In this work, we analyze quantum correlations in $t\bar{t}$ pairs produced in QCD using several quantum information-theoretic measures, including Bell nonlocality, quantum steering, concurrence, and geometric quantum discord. Their dependence on kinematic variables is examined in both the $gg \to t\bar{t}$ and $q\bar{q} \to t\bar{t}$ channels, with convergence toward the $gg \to t\bar{t}$ dominated regime in the ultra-relativistic limit ($β= 1$). We also investigate the effect of three effective decoherence channels (AD, PD, and PF). The AD and PD channels lead to a monotonic degradation of correlations as the decoherence parameter $p$ increases, while the PF channel exhibits a symmetric behavior around $p=1/2$. The impact of these channels on quantum teleportation is analyzed, showing that it remains above the classical threshold of $2/3$ even in the presence of noise. These results indicate that certain quantum resources can persist despite decoherence, opening new perspectives at the interface of quantum information and particle physics.
Characterizing quantum correlations and quantum teleportation in gg→ttˉ and qqˉ→ttˉ processes under noisy channels
The measurement of top-quark spin correlations provides a key tool for probing its interactions with high precision. Owing to its extremely short lifetime (τ∼10−25 s), the top quark preserves its spin polarization information, making the ttˉ system an ideal framework for investigating quantum correlations in high-energy physics. In this work, we analyze quantum correlations in ttˉ pairs produced in QCD using several quantum information-theoretic measures, including Bell nonlocality, quantum steering, concurrence, and geometric quantum discord. Their dependence on kinematic variables is examined in both the gg→ttˉ and qqˉ→ttˉ channels, with convergence toward the gg→ttˉ dominated regime in the ultra-relativistic limit (β=1). We also investigate the effect of three effective decoherence channels (AD, PD, and PF). The AD and PD channels lead to a monotonic degradation of correlations as the decoherence parameter p increases, while the PF channel exhibits a symmetric behavior around p=1/2. The impact of these channels on quantum teleportation is analyzed, showing that it remains above the classical threshold of 2/3 even in the presence of noise. These results indicate that certain quantum resources can persist despite decoherence, opening new perspectives at the interface of quantum information and particle physics.
As the most massive particle in the Standard Model, the top quark's exceptionally short lifetime preserves its spin polarization information through direct decay, making it an ideal system for probing quantum correlations in high-energy physics. In this letter, we presents a comprehensive investigation of quantum correlations in top quark-antiquark pairs produced through QCD. We employ multiple quantum information theoretic measures including quantum mutual information, relative entropy of coherence, complete complementarity relations, and the intrinsic relationship, establishing their dependence on kinematic variables. Furthermore, we find that for quarks and gluons initial mixing, as the probability of gluons Wgg increases, the maximum of the left-hand side of the intrinsic relation also increases. We thus believe the current findings are beneficial to insight into the systemic quantumness in QCD.
Quantum teleportation, entanglement, LQU and LQFI in e+e−→YYˉ processes at BESIII through noisy channels
Quantum teleportation, a protocol that has received extensive and intensive attention in quantum information processing, allows a quantum state to be transferred from one particle to another. In this study, we analytically investigate fidelity (F), logarithmic negativity (LN), local quantum uncertainty (LQU) and local quantum Fisher information (LQFI) as a discord-like measure of quantum correlations in e+e−→YYˉ processes at BESIII through noisy channels, using experimental feasible parameters, where Y and Yˉ refer to the spin-1/2 hyperon and its antihyperon, respectively. Without a dephasing effect, we show that, LN, LQU, and LQFI vanish at φ=±π and are symmetric around φ=π/2. We also explore the LN, LQU, and LQFI for different YYˉ pairs subjected to three distinct types of decoherence channels. Specifically, we show that amplitude damping (AD) and phase damping (PD) lead to a decrease in LN, LQU, and LQFI with an increasing decoherence parameter s. In contrast, the phase flip (PF) channel exhibits symmetric behavior around s=1/2. Besides, we realize for teleportation, optimal fidelity for different hyperon-antihyperon pairs ($ Λ\barΛ$, Ξ0Ξ0ˉ, Ξ−Ξ+ˉ, Σ+Σ−ˉ). We discuss the influence of noisy channels, specifically (AD, PF and PD), on the fidelity of quantum teleportation and on quantum correlations that can exist even beyond entanglement. Furthermore, the results show that the fidelity remains above the classical limit of 2/3 in all three channels, even as the noise increases. This is a significant finding because it shows that not all quantum noise is detrimental. These results can have promising applications in quantum information and particle physics.
Quantum teleportation, a protocol that has received extensive and intensive attention in quantum information processing, allows a quantum state to be transferred from one particle to another. In this study, we analytically investigate fidelity ( F ), logarithmic negativity (LN), local quantum uncertainty (LQU) and local quantum Fisher information (LQFI) as a discord-like measure of quantum correlations in e + e − → Y Y ¯ processes at BESIII through noisy channels, using experimental feasible parameters, where Y and Y ¯ refer to the spin-1/2 hyperon and its antihyperon, respectively. We discuss the dependence of LN, LQU and LQFI on the scattering angle θ for different hyperon-antihyperon pairs ( Λ Λ ¯ , Ξ 0 Ξ 0 ¯ , Ξ − Ξ + ¯ , Σ + Σ − ¯ ), produced by electron-positron annihilation via charmonium decay. Without a dephasing effect, we show that, LN, LQU, and LQFI vanish at φ = ± π and are symmetric around φ = π / 2 . Furthermore, LN reaches its maximum when the scattering angle equals φ = π / 2 , while LQU and LQFI reach their maxima at different angles. We also explore the LN, LQU, and LQFI for different Y Y ¯ pairs subjected to three distinct types of decoherence channels. Specifically, we show that amplitude damping (AD) and phase damping (PD) lead to a decrease in LN, LQU, and LQFI with an increasing decoherence parameter s . In contrast, the phase flip (PF) channel exhibits symmetric behavior around s = 1 / 2 . Besides, we realize for teleportation, optimal fidelity for different hyperon-antihyperon pairs ( Λ Λ ¯ , Ξ 0 Ξ 0 ¯ , Ξ − Ξ + ¯ , Σ + Σ − ¯ ). We discuss the influence of noisy channels, specifically (AD, PF and PD), on the fidelity of quantum teleportation and on quantum correlations that can exist even beyond entanglement. Furthermore, the results show that the fidelity remains above the classical limit of 2/3 in all three channels, even as the noise increases. This is a significant finding because it shows that not all quantum noise is detrimental. These results can have promising applications in quantum information and particle physics.
In distributed quantum computing, quantum networks provide a potential infrastructure for long-range quantum information processing. Controlled quantum teleportation (CQT) is a key practically relevant protocol that can connect two parties on a network and enables a third party, the controller to allow or abort the secure teleportation of an arbitrary single-qubit state between the two parties. We investigate the robustness of a three-qubit GHZ resource under bit-flip, phase-flip, depolarizing, and amplitude-damping noise. Using the Kraus-operator formalism, we characterize the noisy resource through multipartite quantum discord, genuine multipartite concurrence (GMC), localizable entanglement (LE), and CQT fidelity. We also outline a proof-of-concept photonic implementation for preparing the three-qubit GHZ resource and realizing the CQT protocol, which could enable experimental investigation of the effects of noise. Our results show that bit-flip and amplitude-damping noise generally preserve useful mutipartite quantum correlations over broader noise parameter ranges. Interestingly, multipartite discord exhibits freezing under bit-flip noise over a finite parameter regime. Moreover, discord can persist beyond the sudden death of genuine multipartite entanglement, revealing the distinct robustness of nonclassical correlations. We further demonstrate that CQT fidelity which characterizes the performance of CQT can exceed the classical threshold even after GMC vanishes, while LE more closely reflects the operational usefulness of the noisy resource. These findings highlight the complementary roles of quantum correlations and entanglement in assessing the resilience of GHZ-based protocols.
There is a growing interest in investigating top-quark systems using tools from quantum information theory. A key peculiarity of the top quark is that it decays before hadronization or spin decorrelation occurs, thereby preserving its spin information. This unique property enables direct access to spin correlations, making the top quark an ideal candidate for probing fundamental quantum correlations in high-energy physics processes. A wide range of concepts from quantum information theory, such as entanglement, Bell nonlocality, quantum steering, quantum discord, and fidelity, have been investigated in this context. Several of these measures have been employed as diagnostic tools to test the Standard Model and to search for possible signatures of physics beyond. However, the (NAQC) has remained largely unexplored in this context. In this work, we present a detailed investigation of the NAQC in top quark pair production. We employ two complementary NAQC measures based on the l 1 norm and the relative entropy of coherence. We also study the effect of angular averaging on these measures and assess the sensitivity of current LHC spin-correlation measurements to NAQC. Our findings reveal rich coherence structures and highlight NAQC as potentially a novel and complementary quantum signature in high-energy physics systems.
A bstract 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 tt t t ¯ system this extremization can be performed analytically and we provide closed-form formulas for the quantum discord. We demonstrate that with current LHC datasets, quantum discord can be observed at 3 . 6 – 5 . 7 σ , depending on the signal region, with the decay method and can be measured at a precision of 0 . 1 – 0 . 2% with the kinematic method. At the high luminosity LHC, the observation of quantum discord is expected to be > 5 σ using both the decay and kinematic methods and can be measured with a precision of 5% with the decay method and 0 . 05% with the kinematic method. Additionally, we identify the kinematic cuts at the LHC to isolate the tt t t ¯ state that is separable but has non-zero discord. 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.