Quantum Correlations Research Articles

Interplay of Spin Nernst Effect and Entanglement Negativity in Layered Ferrimagnets: A Study via Exact Diagonalization

In this paper, we analyzed the influence of the spin Nernst effect on quantum correlation in a layered ferrimagnetic model. In the study of three-dimensional ferrimagnets, the focus is on materials with a specific arrangement of spins, where the neighboring spins are parallel and the others are antiparallel. The anisotropic nature of these materials means that the interactions between spins depend on their relative orientations in different directions. We analyzed the effect of magnon bands induced by the coupling parameters on entanglement negativity. The influence of the coupling parameters of the topologic phase transition on quantum entanglement is investigated as well. Numerical simulations using the Lanczos algorithm and exact diagonalization for different lattice sizes are compared with the results of spin wave theory.

Charm Physics in the Super τ-Charm Factory

Abstract A high-luminosity Super $\tau$-Charm Factory (STCF) will be a crucial facility for charm physics research, particularly in the precise measurement of electro-weak parameters, measuring $D^0$-$\bar{D}^0$ mixing parameters, investigating CP violation within the charm sector, searching for rare and forbidden decays of charmed hadrons, and addressing other foundational questions related to charmed hadrons. With world-largest charm threshold data, it aims to achieve high sensitivity of studying the strong phase of neutral $D$ mesons using quantum correlation, complementing studies at LHCb and Belle II, and contributing to the understanding of CP violation globally. STCF will also enable world-leading precision in leptonic decays of charmed mesons and baryons, providing constraints on the Cabibbo-Kobayashi-Maskawa matrix and strong force dynamics. Additionally, STCF will explore the charmed hadron spectroscopy. STCF's advanced detector and clean experimental environment will allow for unprecedented precision, helping address key challenges in the Standard Model and searching for potential new physics.

Semidefinite programming relaxations for quantum correlations

Semidefinite programming relaxations for quantum correlations

Conceptual metaphor quantum correlation and radial basis extreme learning for predicting chronic kidney disease

Chronic kidney disease is a progressive condition that often remains unnoticed until substantial kidney damage has occurred, leading to severe complications like nerve damage, pregnancy issues, and potentially fatal kidney failure. Early diagnosis of chronic kidney disease is challenging due to a lack of distinct indicators. To enhance detection, a new machine learning technique called conceptual metaphor quantum mutual correlation and radial basis extreme learning is developed for chronic kidney disease diagnosis. This approach starts by extracting critical terms from unstructured datasets. It then applies quantum mutual information-based feature selection to identify highly correlated feature subsets from both unstructured and structured data. Finally, radial basis extreme learning is used for classification, overcoming imbalanced data and computational issues typical in extreme learning machines. The proposed method demonstrates remarkable accuracy (98 %), precision (88 %), and recall (92 %), surpassing traditional models, and holds significant potential for improving chronic kidney disease detection and treatment.

Masking quantum information in multipartite systems via Fourier and Hadamard matrices ∗ ∗This work was supported by the National Natural Science Foundation of China under Grant No. 12301590 and Natural Science Foundation of Hebei Province under Grant No. A2022210002.

Quantum information masking (QIM) is a crucial technique for protecting quantum data from being accessed by local subsystems. In this paper, we introduce a novel method for achieving 1-uniform QIM in multipartite systems utilizing a Fourier matrix. We further extend this approach to construct an orthogonal array with the aid of a Hadamard matrix, which is a specific type of Fourier matrix. This allows us to explore the relationship between 2-uniform QIM and orthogonal arrays. Through this framework, we derive two distinct 2-uniform quantum states, enabling the 2-uniform masking of original information within multipartite systems. Furthermore, we prove that the maximum number of quantum bits required for achieving a 2-uniformly masked state is 2 n − 1, and the minimum is 2 n−1 + 3. Moreover, our scheme effectively demonstrates the rich quantum correlations between multipartite systems and has potential application value in quantum secret sharing.

Measuring topological invariants for higher-order exceptional points in quantum three-mode systems

Owing to the presence of exceptional points (EPs), non-Hermitian (NH) systems can display intriguing topological phenomena without Hermitian analogs. However, experimental characterizations of exceptional topological invariants have been restricted to second-order EPs (EP2s) in classical or semiclassical systems. We here propose an NH multi-mode system with higher-order EPs, each of which is underlain by a multifold-degenerate multipartite entangled eigenstate. We implement the NH model by controllably coupling a Josephson-junction-based electronic mode to two microwave resonators. We experimentally quantify the topological invariant for an EP3, by mapping out the complex eigenspectra of the tripartite system along a loop surrounding this EP3 in the parameter space. The nonclassicality of the realized topology is manifested by the observed quantum correlations in the corresponding eigenstates. Our results extend research of exceptional topology to fully quantum-mechanical models with multipartite entangled eigenstates.

Non-equilibrium dynamics of symmetry-resolved entanglement and entanglement asymmetry: exact asymptotics in Rule 54*

Abstract Symmetry resolved entanglement and entanglement asymmetry are two measures of quantum correlations sensitive to symmetries of the system. Here we discuss their non-equilibrium dynamics in the Rule 54 cellular automaton, a simple, yet interacting, integrable model. Both quantities can be expressed in terms of the more analytically tractable ‘charged moments’, i.e. traces of powers of a suitably deformed density matrix, via a replica trick. We express them in terms of a tensor network, which we contract in space using a system of local algebraic relations. This gives the asymptotic form for the charged moments, valid in the regime of large but finite time that is shorter than all the relevant subsystem sizes. In this regime the charge moments decay exponentially with the rate given by the leading solution to a cubic equation.

Decoherence Effects on Local Quantum Fisher Information and Quantum Coherence in a Spin‐1/2$1/2$ Ising‐XYZ$XYZ$ Chain

AbstractThis research explores the effects of decoherence on local quantum Fisher information and quantum coherence dynamics in a spin‐1/2 Ising‐XYZ chain model with independent reservoirs at zero temperature. Contrasting these effects with those in the spin‐1/2 Heisenberg XYZ model reveals intricate interactions among quantum coherence, entanglement, and environmental decoherence in spin systems. Analysis of coherence dynamics highlights differences between the original and hybrid models, showcasing increased entanglement due to Ising interactions alongside reduced coherence from environmental redistribution. proves more resilient than coherence in specific scenarios, emphasizing decoherence's varying impacts on quantum correlations. This research underscores the complexity of quantum coherence dynamics and the crucial role of environmental factors in shaping quantum correlations, providing insights into entanglement and coherence behavior under environmental influences and guiding future studies in quantum information processing and correlation dynamics.

Performance of Quantum Correlations and Estimation of Gravitational State under a Joint Thermal-Bosonic Reservoir

Performance of Quantum Correlations and Estimation of Gravitational State under a Joint Thermal-Bosonic Reservoir

Freezing phenomenon in high-dimensional quantum correlation dynamics

Freezing phenomenon in high-dimensional quantum correlation dynamics

Effects of reservoir squeezing on the amplification of quantum correlation and the quantum speed limit

Effects of reservoir squeezing on the amplification of quantum correlation and the quantum speed limit

The Development of a High-Throughput Homonuclear Decoupling HSQC NMR Platform for the Determination of 10 Sex Hormones in Animal-Source Food and Medicines

Owing to their endocrine disruption effect, the hormone levels in animal-source food and medicines need to be efficiently and accurately quantified by a reliable analytical method. In the current study, by using a homonuclear decoupling and heteronuclear single quantum correlation (HSQC) experiment, coupled with non-uniform sampling (NUS) that was used to shorten the experimental time, we developed a method to quantify 10 hormone residues in animal-source products. This method was validated following the guidelines of USP–NF 2022. The application of the homonuclear decoupling (HD) technique to conventional HSQC yielded 2D spectra that exhibited excellent signal separation and specificity. For all the tested hormones, good linearity with correlation coefficients of more than 0.99 was observed in the linear range of 0.2–6 mg/0.6 mL. Satisfactory precision and recoveries of spiked animal samples were also obtained. Finally, the method was applied in residue determination of 10 hormones in real animal-source samples at the ug/g level.

Role of coherence in many-body Quantum Reservoir Computing

Quantum Reservoir Computing (QRC) offers potential advantages over classical reservoir computing, including inherent processing of quantum inputs and a vast Hilbert space for state exploration. Yet, the relation between the performance of reservoirs based on complex and many-body quantum systems and non-classical state features is not established. Through an extensive analysis of QRC based on a transverse-field Ising model we show how different quantum effects, such as quantum coherence and correlations, contribute to improving the performance in temporal tasks, as measured by the Information Processing Capacity. Additionally, we critically assess the impact of finite measurement resources and noise on the reservoir’s dynamics in different regimes, quantifying the limited ability to exploit quantum effects for increasing damping and noise strengths. Our results reveal a monotonic relationship between reservoir performance and coherence, along with the importance of quantum effects in the ergodic regime.

Bell Test of Quantum Entanglement in Attosecond Photoionization

Attosecond physics enables the study of ultrafast coherent electron dynamics in matter upon photoexcitation and photoionization, revealing spectacular effects such as hole migration and coherent Auger dynamics in molecules. In the photoionization scenario, there has been a strong focus on probing the physical manifestations of internal quantum coherence within the individual parent ion and photoelectron systems. However, quantum correlations between these two subsystems emerging from attosecond photoionization events have thus far remained much more elusive. In this work, we design theoretically and model numerically a direct probe of quantum entanglement in attosecond photoionization in the form of a Bell test. We simulate from first principles a Bell test protocol for the case of noble gas atoms photoionized by ultrashort, circularly polarized infrared laser pulses in the strong-field regime predicting robust violation of the Bell inequality. This theoretical result paves the way for the direct observation of entanglement in the context of ultrafast photoionization of many-electron systems. Our work provides a novel perspective on attosecond physics directed toward the detection of quantum correlations between systems born during attosecond photoionization and unraveling the signatures of entanglement in ultrafast coherent molecular dynamics, including in the chemical decomposition pathways of molecular ions. Published by the American Physical Society 2024

Robustness of quantum correlation in quantum energy teleportation

In this article, we explore a feedback-control protocol in different quantum field theories (QFTs) to study the quantum correlation in nonunitary evolution of quantum systems. Traditional studies on QFTs focus on quantum entanglement of pure states under the unitary evolution, however, we examine quantum correlation in mixed states using quantum energy teleportation (QET), which is an energy transfer protocol by utilizing ground state entanglement, and introduce quantum discord as a measure. QET involves a midcircuit measurement, which disrupts pure state entanglement. Despite this, our analysis demonstrates that quantum discord maintains the correlation throughout the QET process. We conducted numerical analyses with benchmark models including the Nambu-Jona-Lasinio (NJL) model, revealing that quantum discord consistently acts as an order parameter for phase transitions. The model is extended in a way that it has both the chiral chemical potential and the chemical potential, which are useful to study the phase structures mimicking the chiral imbalance between left- and right- quarks coupled to the chirality density operator. In all cases we studied, the quantum discord behaved as an order parameter of the phase transition. Published by the American Physical Society 2024

Cross Peaks on Two-Dimensional Optical Spectra Arising from Quantum Cross-Correlation Functions.

Cross peaks on 2D optical spectra are indicative of interactions between molecular excitonic states. Currently, the two conventional assignments of cross peaks are direct coupling and population transfer between excitonic states. Here, we show that there is another possible source of cross peaks. We theoretically demonstrate that for a model comprising two nondirectly interacting excitons or two-level systems (TLSs), cross peaks can arise if there is a complex-valued or quantum frequency-gap cross-correlation function between the two TLSs. Considering only real-valued or classical cross-correlation functions will result in no cross peaks. We derive and validate the mathematical expressions describing such cross peaks. We then simulate the 2D electronic spectra of an example model system comprising nondirectly interacting TLSs whose quantum cross-correlation functions arise from coupling to a common overdamped Brownian oscillator mode. We show that there are clear observational differences between such quantum correlation cross peaks with conventional direct coupling and population transfer cross peaks.

Nonlocal correlations and entanglement in two coupled double quantum dots under external magnetic field

Abstract Double quantum dot (DQD) systems are highly regarded as promising candidates for advancements in the fields of quantum computing and quantum information processing. In this work, we investigate the behaviour of quantum correlations (QCs) in a system of two DQDs, AlGaAs/GaAs under various parameters such as temperature, energy offsets, coupling strength, and magnetic fields. We employ uncertainty-induced nonlocality and Bell nonlocality to quantify QC and logarithmic negativity to measure entanglement in the considered physical system. The findings demonstrate that QCs are significantly influenced by noisy equilibrium temperature and system parameters. In particular, lower temperatures enhance QCs, whereas higher temperatures result in a decrease due to thermal effects. In addition, the magnetic fields have a profound influence on the conditions of resonance. We also show that maximum QCs occur at resonance conditions with no energy offset between each DQD. However, introducing an energy offset or too-strong coupling reduces these correlations. Finally, our findings provide an understanding of the behaviour of entanglement and quantum nonlocality in DQD systems, offering potential implications for quantum technologies.

Experimental investigation of quantum correlations under restricted distrust in a semi-device-independent framework

Experimental investigation of quantum correlations under restricted distrust in a semi-device-independent framework

Witnessing Entanglement and Quantum Correlations in Condensed Matter: A Review

AbstractThe detection and certification of entanglement and quantum correlations in materials is of fundamental and far‐reaching importance, and has seen significant recent progress. It impacts both the understanding of the basic science of quantum many‐body phenomena as well as the identification of systems suitable for novel technologies. Frameworks suitable to condensed matter that connect measurements to entanglement and coherence have been developed in the context of quantum information theory. These take the form of entanglement witnesses and quantum correlation measures.The underlying theory of these quantities, their relation to condensed matter experimental techniques, and their application to real materials are comprehensively reviewed. In addition, their usage in, e.g., protocols, the relative advantages and disadvantages of witnesses and measures, and future prospects in, e.g., correlated electrons, entanglement dynamics, and entangled spectroscopic probes, are presented. Consideration is given to the interdisciplinary nature of this emerging research and substantial ongoing progress by providing an accessible and practical treatment from fundamentals to application. Particular emphasis is placed on quantities accessible to collective measurements, including by susceptibility and spectroscopic techniques. This includes the magnetic susceptibility witness, one‐tangle, concurrence and two‐tangle, two‐site quantum discord, and quantum coherence measures such as the quantum Fisher information.

Quantum correlations and parameter estimation for two superconducting qubits interacting with a quantized field

In the present manuscript, we introduce a quantum system of two superconducting qubits (S–Qs) interacting with a quantized field under the influence of the Kerr nonlinear medium and Ising interaction. We formulate the Hamiltonian of the quantum model and determine the density operator of whole quantum system as well as quantum subsystems. We examine the dynamics of the quantumness measures for subsequent times including the S–Qs entanglement, S–Qs-field entanglement and quantum Fisher information in relation to the system parameters. Finally, we display the connection among the measures of quantumness during the time evolution.