arXiv subjects

Cong-Feng Qiao

Publications and source records attributed to Cong-Feng Qiao.

At least 19 recordsLinked to original sources

arXiv2026

Where to find $X(17)$?

The Atomki group puts forward the hypothesis of an $X(17)$ particle to explain its anomaly observation in ${^{8}\text{Be}^{*}} \to {^{8}\text{Be}} e^+e^-$ transition. Utilizing experimental results from the Atomki experiments, measurements of the electron's anomalous magnetic moment (AMM), the parity-violating Møller scattering experiment, the NA64 experiment, the KLOE-2 experiment, and the PADME experiment, we derive constraints on the $Xee$ coupling of the hypothetical $X(17)$ boson to electrons. A joint $χ^2$ analysis of the electron's AMM (Cs and Rb measurements) and the parity-violating Møller scattering yields two mutually exclusive solutions. The Cs and Rb AMM constraints restrict the combination $(\varepsilon_e^v)^2-5(\varepsilon_e^a)^2$ with opposite signs. Cs+Møller combination favours a dominant axial-vector coupling $|\varepsilon_e^a|\approx5.3\times10^{-4}\gg|\varepsilon_e^v|$, whereas Rb+Møller favours a dominant vector coupling $|\varepsilon_e^v|\approx6.9\times10^{-4}\gg|\varepsilon_e^a|$. The Møller bound suppresses the subdominant coupling for both solutions. Incorporating NA64 and KLOE-2 limits on $(\varepsilon_e^v)^2+(\varepsilon_e^a)^2$ introduces mild tension for the Cs+Møller solution, while the Rb+Møller solution remains nearly unchanged.

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arXiv2026

Geometric Optimization over Quantum State Spaces: Tight Uncertainty Relations and Resource Certification

Determining the fundamental limits of nonlinear functionals of quantum measurement statistics is a crucial yet generally intractable nonconvex optimization problem. We introduce a generic support-function-based outer-approximation framework for solving concave-minimization (or convex-maximization) problems over the quantum state space. By mapping the problem onto a reduced $\mathcal{Z}$ space, we characterize the exact quantum boundary through supporting half space derived from the largest eigenvalues of effective observables. This yields an effective method that produces tight bounds for general measurements in finite-dimensional quantum systems with preassigned numerical precision. As an initial application, we recover the exact variance-based uncertainty relations of [PRL \textbf{119}, 170404 (2017)] and efficiently compute optimal entropic uncertainty relations (EURs). Our results reveal that standard analytical and majorization-based EUR bounds are fundamentally loose for generic measurements, and we show that the resulting exact bounds directly enhance quantum steering detection under asymmetric settings. We further apply the framework to determine the maximal athermality resource certifiable from a restricted measurement scenario. Our method thus provides a universal computational tool for exploring the boundaries of quantum state space and the limits of quantum resources.

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arXiv2026

Fixed-Point Bifurcations and Path-Information Bounds in Nonlinear Exceptional-Point Sensing

Nonlinear exceptional points (NEPs) were proposed to circumvent the noise--responsivity cancellation that limits linear exceptional-point sensors. At an NEP, the stationary frequency response can be singular while the Hamiltonian Petermann factor remains finite, suggesting a genuine signal-to-noise ratio (SNR) enhancement. Yet recent model-specific analyses of nonlinear fluctuations have reached conflicting conclusions. We prove that any singular stationary frequency response requires a fixed-point bifurcation of the nonlinear dynamics. In local fluctuation regimes, the singularities in responsivity and long-time frequency uncertainty are both set by the critical relaxation rate, leading to exact cancellation in the SNR and precluding any divergent enhancement. Furthermore, we derive a path-information bound that applies across both local and nonlinear fluctuation regimes and places a finite ceiling on the long-time SNR enhancement. Notably, this upper bound is attainable in the local fluctuation regime, implying that frequency readout under such parameter settings is information-optimal.

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arXiv2026

True Leptonium ($l^+ l^-$) Production in UPC Triphoton Interaction

True leptonium states ($l^+ l^-$) are compact pure QED systems, first theoretically predicted eight decades ago. Although considerable efforts have been devoted to their search, only positronium has been experimentally confirmed shortly after its theoretical prediction. By contrast, dimuonium ($μ^+ μ^-$) and tauonium ($τ^+ τ^-$) remain unobserved to date, partly due to their low production yields. In this work, we investigate ortho-leptonium production through triphoton interactions in ultraperipheral heavy-ion collisions (UPCs). Two photons originate from different ions in one beam, while the third is supplied by an ion in the opposing beam. Within the equivalent photon approximation, we compare continuum dimuon and $J/ψ$ production with UPC measurements and evaluate ortho-leptonium production at the LHC and FCC. The results illustrate the possible role of triphoton fusion in leptonium production and the sensitivity of the calculated rates to the low-energy photon input.

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arXiv2026

Radial Coarse Graining Restores Vacuum Majorization in Wigner Phase Space

Quantum uncertainty limits how strongly Wigner functions can concentrate in phase space. It is commonly conjectured that the vacuum Wigner function continuously majorizes that of any Wigner-positive state. However, by constructing Wigner-positive states whose localized quantum coherence lowers their Wigner entropy below the vacuum value, we show that this conjecture is incorrect. We restore vacuum majorization at finite resolution by integrating single-mode Wigner functions over concentric radial energy shells, obtaining probability vectors majorized by that of the vacuum for all Wigner-positive states and for Wigner-negative states with non-negative shell weights. Anchoring these shells to a fixed oscillator frame breaks affine symplectic invariance, rendering this relation strict for every non-vacuum Gaussian pure state. For Wigner-negative states, the persistence of negative shell weights defines a radial negativity scale with Airy-edge semiclassical asymptotics for highly excited Fock states. Operationally, we combine the majorization relation with partial transposition to obtain a two-mode entanglement criterion directly evaluable from radially binned joint homodyne outcomes without state reconstruction.

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arXiv2026

Decipher the nature of glueball candidate $X(2370)$

As a unique form of matter composed entirely of gauge bosons, glueballs are an important low-energy prediction of QCD. After decades of searches, the BESIII Collaboration recently suggested that $X(2370)$ may contain a dominant glueball component, based largely on evidence that it is approximately a flavor singlet. Recognizing that flavor-singlet character does not uniquely identify a glueball, we perform a comprehensive analysis using available mass, flavor-singlet, and decay constraints. We find that three flavor-singlet configurations-hybrid meson, tetraquark state, and trigluon glueball-can satisfactorily reproduce the existing experimental data. Among these possibilities, the hybrid structure best describes the measured three-pseudoscalar decay ratios. To ultimately pin down the dominant structure of $X(2370)$, we propose measuring the decay-width ratios $a_0(1450)π/[K_0^*(1430)\bar K+\mathrm{c.c.}]$ and $ϕϕ/[b_1(1235)ρ]$, which can exclusively distinguish these three scenarios.

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arXiv2026

Leggett-type inequalities for testing nonlocal realism in multipartite systems

Nonlocal realism represents the last classical cornerstone in conflict with quantum theory, and has been shown to be largely untenable in bipartite systems [Nature 446, 871 (2007); Nature Physics 4, 681 (2008)]. We extend the Leggett-type nonlocal realistic model to arbitrary N-partite systems with polarizer settings, and derive rigorous inequalities that distinguish quantum predictions from nonlocal realistic theories. The derivation yields a fundamental double inequality that is universally valid, from which the Leggett-type bounds follow under specific measurement settings. As an illustration, we demonstrate quantum violations of these inequalities for Greenberger-Horne-Zeilinger (GHZ) states, with maximal violation 2(\sqrt{5}+1). Our results show that nonlocal realism in multipartite systems is experimentally testable.

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arXiv2026

Exclusive Leptonium Electroproduction

Purely leptonic bound states provide precision probes of QED. Positronium $(e^+e^-)$ and muonium $(μ^+e^-)$ have long been observed, whereas dimuonium $(μ^+μ^-)$ and tauonium $(τ^+τ^-)$ remain undiscovered. We study exclusive vector-leptonium electroproduction in $ep$ collisions within nonrelativistic QED. We include the Bethe--Heitler and double deeply virtual Compton scattering contributions and their interference, and calculate the NLO QCD hard-scattering kernels entering the dominant Compton form factor $\Hcal$ within collinear GPD factorization. The NLO QCD correction to the DDVCS contribution changes from a strong suppression at low photon virtuality to a sizable enhancement as the lower virtuality cut is raised, with the gluon channel providing the dominant contribution. Bethe--Heitler production dominates the exclusive rate, supporting dedicated dimuonium searches at the EIC and JLab, with larger samples expected at higher-energy electron--proton colliders. The much larger positronium samples provide a high-statistics environment for precision QED studies, whereas tauonium production remains strongly suppressed.

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arXiv2026

Baryons and baryoniums in the perspective of QCD sum rules

Following the experimental confirmation of tetraquark and pentaquark states, the search for hexaquark states has emerged as a new frontier in hadron physics. The recent observation of $X(1840)$ and $X(1880)$ by BESIII collaboration has provided evidence for the predicted $p\bar{p}$ bound states. Such baryon-antibaryon configurations, encompassing both bound states and resonances, are commonly referred to as baryoniums and are regarded as promising hexaquark candidates. In this article, we provide a comprehensive review of the investigations into baryonium states and their constituents, i.e., baryons, within the framework of QCD sum rules. We delineate the fundamental calculation procedures of this method to facilitate its practical application and benchmark the theoretical predictions against alternative models as well as the latest experimental data.

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arXiv2026

Nonlocal Topological Maxwell Demon Teleporting Ergotropy via Surface-Code Quantum Error Correction

Surface-code quantum error correction has recently achieved logical error rates below the physical threshold on superconducting processors, establishing topologically ordered states as experimentally accessible resources. Whether these resources can support thermodynamic operations beyond fault-tolerant computation remains open. We introduce a nonlocal Maxwell demon protocol that transfers ergotropy between spatially separated quantum batteries using only local operations and classical communication over a shared surface code. Alice expends ergotropy to encode a logical qubit and transmits a classical syndrome record to Bob, who decodes via minimum-weight perfect matching and conditionally charges his battery, with no direct energy exchange across the channel. Active syndrome monitoring exponentially suppresses logical errors below the topological threshold $p_{\rm th} \approx 0.013$, converting physical qubits directly into recoverable ergotropy. For finite-size codes at distance $L = 7$, net extracted work changes sign at a thermodynamic critical error rate $p_c \approx 0.014 > p_{\rm th}$, a physically significant finite-size effect relevant to near-term devices. Causality enforces an irreducible quadratic infrastructure cost $W_{\rm bulk} \propto N^2$, strictly satisfying the second law at all separations and defining a fundamental thermodynamic horizon $N_{\rm max} \approx 78$ beyond which positive net work extraction is impossible regardless of code distance or decoder quality.

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arXiv2026

Mass Spectra of $Λ_Q\barΣ_Q$ Hexaquark States in QCD Sum Rules

Recently, the BESIII Collaboration indicate that no $Λ_c\barΣ_c$ bound-state with a mass near threshold in the range $4715$--$4735~\mathrm{MeV}$ was observed. In order to determine the plausible mass region of the states in this structure, we calculate the mass spectrum of the $Λ_c\barΣ_c$ configuration with the method of QCD sum rules. Two linearly independent interpolating currents are constructed, and contributions from nonperturbative condensates up to dimension 12 are included in the numerical results. Consequently, we obtain the masses of the candidate states with quantum numbers $J^P = 0^-,\,0^+,\,1^-,\,1^+$. Our results show that the central values of the $Λ_c\barΣ_c$ ground-state masses lie around the $5.8~\mathrm{GeV}$ region, which do not support them as bound states and consistent with the findings reported by the BESIII Collaboration. Furthermore, we compute the mass spectrum of the $Λ_b\barΣ_b$ states with quantum numbers $J^P = 0^-,\,0^+,\,1^-,\,1^+$, which could be served as hidden-bottom candidates in the experimental detecting.

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arXiv2026

Witness High-Dimensional Quantum Steering via Majorization Lattice

Quantum steering enables one party to influence another remote quantum state by local measurement. While steering is fundamental to many quantum information tasks, the existing detection methods in the literature are mainly constrained to either specific measurement scenario or low-dimensional systems. In this work, we propose a majorization lattice framework for steering detection, which is capable of exploring the steering in arbitrary dimension and measurement setting. Steering inequalities for two-qubit states, high-dimensional Werner states and isotropic states are obtained, which set even stringent bars than what has been reached yet. Notably, the known high-dimensional results turn out to be some kind of approximate limits of the new approach.

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arXiv2026

Spectrum of Light Hexaquark States in Triquark-antitriquark Configuration

To understand the nature of $X(2075)$ and $X(2085)$ observed by the BESIII collaboration in the $p\barΛ$ system, we systematically investigate the possibility that these states are compact hexaquark with triquark-antitriquark configurations for the first time. Within the framework of QCD sum rules, the mass spectrum and decay constants of such hexaquark states with quantum numbers $J^P=0^-, 0^+, 1^-, 1^+$ are studied. Consequently, six independent and nondegenerate hexaquark candidates are obtained, among which two $J^P = 1^-$ states exhibit masses consistent with $X(2075)$, while the two $J^P = 1^+$ states differ markedly from the mass of $X(2075)$ or $X(2085)$. The remaining two states with $J^P = 0^+$ and $0^-$ may serve as predictions for potential compact hexaquark configurations. Furthermore, the possible decay modes of these hexaquark states are analyzed, which could be the experimental signatures for their identification.

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arXiv2026

Scalable Repeater Architecture for Long-Range Quantum Energy Teleportation in Gapped Systems

Quantum Energy Teleportation (QET) constitutes a paradigm-shifting protocol that permits the activation of local vacuum energy through the consumption of pre-existing entanglement and classical communication. Nevertheless, the implementation of QET is severely impeded by the fundamental locality of gapped many-body systems, where the exponential clustering of ground-state correlations restricts energy extraction to microscopic scales. In this work, we address this scalability crisis within the framework of the one-dimensional anisotropic XY model. We initially provide a rigorous characterization of a monolithic measurement-induced strategy, demonstrating that while bulk projective measurements can theoretically induce long-range couplings, the approach is rendered physically untenable by exponentially diverging thermodynamic costs and vanishing success probabilities. To circumvent this impasse, we propose and analyze a hierarchical quantum repeater architecture adapted for energy teleportation. By orchestrating heralded entanglement generation, iterative entanglement purification, and nested entanglement swapping, our protocol effectively counteracts the fidelity degradation inherent in noisy quantum channels. We establish that this architecture fundamentally alters the operational resource scaling from exponential to polynomial. This proves, for the first time, the physical permissibility and computational tractability of activating vacuum energy at arbitrary distances. The significance lies not in net energy gain, but in establishing long-range QET as a viable protocol for remote quantum control and resource distribution.

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arXiv2026

Ascertaining higher-order quantum correlations in high energy physics

Nonlocality is a peculiar nature of quanta and it stands as an important quantum resource in application. Yet mere linear property of it, viz. the first order in moment, has been explored through various inequalities. Noticing the vast higher-order regime unexplored, in this study we investigate the higher-order quantum correlations in entangled hyperon-antihyperon system, which may be generated massively in charmonium decays. A new type of Clauser-Horne inequality for statistical cumulants and central moments is formulated. We find that a significant violation of the third-order constraint, indicating the existence of higher-order correlation, exists in hyperon-antihyperon system and can be observed in high energy physics experiments, like BESIII and Belle II. Notably, the violation manifests more in higher energy systems of the $Λ\barΛ$ pair against the kinematic contamination of timelike events.

quant-ph↗

arXiv2026

The Spectra of $p\barΛ$ and $p\barΣ$ Hexaquark States

Motivated by the observation of the $J^P = 1^+$ resonance $X(2085)$ in the $p\barΛ$ system by the BESIII collaboration, we studied the molecular states of hexaquarks $p\barΛ$ and $p\barΣ$ with baryon-antibaryon structures within the framework of the QCD sum rules. Non-perturbative contributions up to dimension 13 were considered in our analysis. The results indicate the existence of six possible molecular states $p\barΛ$ and $p\barΣ$, with quantum numbers $J^{P}=0^{-}, 0^{+}, 1^{-}$. Consequently, the current sum rule results do not support the interpretation of $X(2085)$ as a $p\barΛ$ or $p\barΣ$ molecular state. On the other hand, we find that the masses of the proposed $p\barΛ$ and $p\barΣ$ structures with $J^{P} = 1^{-}$ are in the vicinity of observed $X(2075)$, which implies that the nature of this state needs more invistigations. Moreover, the possible decay modes of the concerned hexaquark states are analyzed.

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arXiv2025

Conditions for Quantum Violation of Macrorealism in Large-spin Limit

This study investigates the emergence of macroscopic classical behavior from quantum foundations via the entropic Leggett--Garg inequality. We introduce a geometric framework for deriving entropic Leggett--Garg inequalities with higher-order temporal correlations and demonstrate their advantages over conventional formulations. Numerical analyses show that entropic Leggett--Garg inequalities offer a robust and complementary criterion to standard approaches, providing a transparent information theoretic interpretation that facilitates the characterization of coherent quantum processes. By applying the WKB approximation, we prove that violations for maximally mixed states remain bounded by a constant in the macroscopic limit, indicating that macrorealism dominates in generic parameter regimes. We further explain previously reported maximal violations at specific parameter regimes as a consequence of the breakdown of the WKB approximation. Our findings indicate that quantum and classical descriptions remain macroscopically incompatible, while violations persist only in fine-tuned regimes, clarifying the conditions for detecting macroscopic quantum phenomena.

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arXiv2025

QCD sum rule predictions on gluonic tetraquark states with $J^{PC}=0^{+-},0^{--}$ and $1^{\pm \pm}$

In this work, we present a systematic calculation of the mass spectrum for tetraquark hybrid states, focusing on the $8_{[c\bar{c}]}\otimes 8_{[G]}\otimes 8_{[c\bar{c}]}$ color configuration, within the framework of QCD sum rules. As an extension of our previous work on $0^{++}$ and $0^{-+}$ states, we now construct 18 distinct interpolating currents with $J^{PC} = 0^{+-}$, $0^{--}$, and $1^{\pm\pm}$. Using operator product expansion (OPE) techniques and including nonperturbative contributions up to dimension six, we obtain key results: for the $0^{+-}$, $1^{--}$, and $1^{-+}$ states, the predicted masses lie in the range of $7.2-7.3$ GeV, while the $1^{+-}$ and $1^{++}$ states have slightly lower masses, between 6.9 and 7.1 GeV. These predictions provide strong support for the possible existence of an $8_{[c\bar{c}]}\otimes 8_{[G]}\otimes 8_{[c\bar{c}]}$ component within the di-$J/ψ$ structure reported by LHCb. Moreover, our analogous calculations for tetrabottom hybrid states yield mass ranges of $19.4-19.5$ GeV (for $0^{+-}$, $1^{--}$, and $1^{-+}$) and $19.2-19.3$ GeV (for $1^{+-}$ and $1^{++}$), offering crucial references for future searches.

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