Showing papers on "Concurrence published in 2023"
TL;DR: In this paper , the authors exploit the potential of randomized measurements in order to probe the amount of entanglement contained in multiparticle quantum systems as quantified by the multiparticle concurrence.
Abstract: Randomized measurements constitute a simple measurement primitive that exploits the information encoded in the outcome statistics of samples of local quantum measurements defined through randomly selected bases. In this work we exploit the potential of randomized measurements in order to probe the amount of entanglement contained in multiparticle quantum systems as quantified by the multiparticle concurrence. We further present a detailed statistical analysis of the underlying measurement resources required for a confident estimation of the introduced quantifiers using analytical tools from the theory of random matrices. The introduced framework is demonstrated by a series of numerical experiments analyzing the concurrence of typical multiparticle entangled states as well as of ensembles of output states produced by random quantum circuits. Finally, we examine the multiparticle entanglement of mixed states produced by noisy quantum circuits consisting of single- and two-qubit gates with non-vanishing depolarization errors, thus showing that our framework is directly applicable in the noisy intermediate-scale regime.
1 citations
01 Feb 2023
TL;DR: In this paper , the authors investigate the chiral quantum walk (CQW) as a mechanism for an entanglement transfer on a triangular chain structure and evaluate the success of the state transfer.
Abstract: We investigate the chiral quantum walk (CQW) as a mechanism for an entanglement transfer on a triangular chain structure. We specifically consider two-site spatially entangled cases in short-time and long-time regimes. Using the concurrence as an entanglement measure; fidelity, and the Bures distance as the measure of the quality of the state transfer, we evaluate the success of the entanglement transfer. We compare the entangled state transfer time and quality in CQW against a continuous-time quantum random walk. We also observe the effect of mixed states on the entanglement transfer quality.
1 citations
01 Jan 2023
28 May 2023
TL;DR: In this paper , the authors present a concrete physical diagrammatic model of entanglement characterization and measure with its underlying discrete phase-space physics, which is readily extendable to multi-partite systems of qubits, as can be deduced from the physical inverter-chain link model.
Abstract: In contrast to abstract statistical analyses in the literature, we present a concrete physical diagrammatic model of entanglement characterization and measure with its underlying discrete phase-space physics. This paper serves as a pedagogical treatment of this complex subject of entanglement measures. We review the important inherent concurrence property of entangled qubits, as well as underscore its emergent qubit behavior. From the discrete phase space point of view, concurrence translates to translation symmetry of entangled binary systems in some quantitative measure of entanglement. Although the focus is on bipartite system, the notion is readily extendable to multi-partite system of qubits, as can easily be deduced from the physical inverter-chain link model. A diagrammatic analysis of the entanglement of formation for any multi-partite qubit system is given
TL;DR: In this article , a two-qubit system is coupled with a decoherence channel, and the quantum discord and concurrence are visually characterized and detected by employing the Quantum Steining ellipsoid (QSE).
Abstract: Abstract Quantum steering ellipsoid (QSE) can faithfully characterize arbitrary bipartite state, and provide a new method to visually investigate and capture various quantum nonlocalities. Note that the dissipation of quantum nonlocalities can be accelerated by the coupling between the system and the decoherence channel, which induces great challenges in detecting quantum nonlocalities. Herein, considering the scenario in which the subsystem of a two-qubit system is coupled with a decoherence channel, the quantum discord (QD) and concurrence are visually characterized and detected by employing the QSE. The results reveal that the QSE y and z semiaxes are responsible for the traits of the QD and concurrence under the bit flip channel. The x and y semiaxes dominate and visualize the QD and concurrence under the phase damping channel. Of particular note is that one can realize the detections of the QD and concurrence via the shape of the QSE. To be clearer, the disappearance of the QD can be ascertained according to a needle-shaped QSE or a vanishing QSE in the Bloch sphere. In contrast, one can witness the concurrence if the total semiaxis length is greater than one. Beyond this, our results visually reveal that quantum entanglement is a stronger quantum nonlocality than the QD from the perspective of geometry, and thus deepens the understanding of the quantum nonlocality.
TL;DR: In this article , the authors investigated a spin−1/2 quantum Heisenberg model with disordered exchange couplings and magnetic fields and numerically investigated the competition between disorder and correlation in a protocol involving the transfer of a magnon state from one end of the chain to the other.
31 Jan 2023
TL;DR: In this article , a scheme for fast quantum-state synthesis using exceptional point engineering in a lossy chain of three superconducting resonators is presented, where the authors theoretically find that the rich physics of EPs can be used to identify regions in the parameter space that favor a fast and quasi-stable transfer of squeezing and entanglement, or a fast reset of the system.
Abstract: The interplay between coherent and dissipative dynamics required in various control protocols of quantum technology has motivated studies of open-system degeneracies, referred to as exceptional points (EPs). Here, we introduce a scheme for fast quantum-state synthesis using exceptional-point engineering in a lossy chain of three superconducting resonators. We theoretically find that the rich physics of EPs can be used to identify regions in the parameter space that favor a fast and quasi-stable transfer of squeezing and entanglement, or a fast reset of the system. For weakly interacting resonators with the coupling strength $g$, the obtained quasi-stabilization time scales are identified as $1/(2\sqrt{2}g)$, and reset infidelities below $10^{-5}$ are obtained with a waiting time of roughly $6/g$ in the case of weakly squeezed resonators. Our results shed light on the role of EPs in multimode Gaussian systems and pave the way for optimized distribution of squeezing and entanglement between different nodes of a photonic network using dissipation as a resource.
TL;DR: In this article , the authors investigate entanglement mediated by DC current induced non-reciprocal graphene plasmon polaritons and use concurrence as a measure of concurrence.
Abstract: We investigate entanglement mediated by DC current induced nonreciprocal graphene plasmon polaritons. Nonreciprocal systems are ideal for the enhancement, control, and preservation of entanglement due to the potential for unidirectional beam-like wave propagation, i.e., efficiently transporting photons from one emitter to another. Using a quantum master equation and three-dimensional Green's function analysis, we investigate a system consisting of two two-level emitters dominantly interacting via electric current induced nonreciprocal plasmonic modes of a graphene waveguide. We use concurrence as a measure of entanglement. We show that nonreciprocal graphene plasmon polaritons are a promising candidate to generate and mediate concurrence, where it is shown that there is good enhancement and control of entanglement over vacuum, which is beneficial for the broad applications of entanglement as a quantum resource. We believe our findings contribute to the development of quantum devices, enabling efficient and tunable entanglement between two-level systems, which is a central goal in quantum technologies.
TL;DR: In this article , the authors study general monogamy and polygamy relations based on the power of entanglement measures and the power power of assisted entanglements, respectively, and illustrate that these polygamous relations are tighter than the inequalities in the article Jin et al. (Quantum Inf Process 19:101, 2020).
Abstract: Monogamy and polygamy are important properties of entanglement, which characterize the entanglement distribution of multipartite systems. We study general monogamy and polygamy relations based on the $$\alpha $$ th $$(0\le \alpha \le \gamma )$$ power of entanglement measures and the $$\beta $$ th $$(\beta \ge \delta )$$ power of assisted entanglement measures, respectively. We illustrate that these monogamy and polygamy relations are tighter than the inequalities in the article Jin et al. (Quantum Inf Process 19:101, 2020), so that the entanglement distribution can be more precisely described for entanglement states that satisfy stronger constraints. For specific entanglement measures such as concurrence and the convex-roof extended negativity, by applying these relations, one can yield the corresponding monogamous and polygamous inequalities, which take the existing ones in the articles Zhu and Fei (Quantum Inf Process 18:23, 2019) and Jin et al. (Quantum Inf Process 18:105, 2019) as special cases. More details are presented in the examples.
TL;DR: In this paper , the effect of thermal bath on quantum correlations induced by the gravitational interaction in the weak field limit between two massive cat states, called gravitational cat (gravcat) states, was investigated.
Abstract: We consider the effect of a thermal bath on quantum correlations induced by the gravitational interaction in the weak field limit between two massive cat states, called gravitational cat (gravcat) states. The main goal of this paper is to provide a good understanding of the effects of temperature and several parameters in the entanglement (measured by the concurrence) and quantum coherence (measured by the l1-norm that is defined from the minimal distance between the quantum state and the set of incoherent states) which are derived from the thermal quantum density operator. Our results show that the thermal concurrence and l1-norm can be significantly optimized by increasing the masses or decreasing the distance between them. We investigate and discuss the behavior of these quantities under temperature variations in different regimes, including some that are expected to be experimentally feasible in the future. In particular, we observe that thermal fluctuations raise non-entangled quantum correlations when entanglement suddenly drops.
TL;DR: In this article , the authors investigated the monogamy relations for multi-qubit systems and established tighter inequalities for their α-th power than those in all the existing ones, and also illustrate the tightness of their results for some classes of quantum states.
Abstract: The entanglement in multipartite quantum system is hard to characterize and quantify, although it has been intensively studied in bipartite systems. The monogamy of entanglement, as a special property of multipartite systems, shows the distribution of entanglement in the system. In this paper, we investigate the monogamy relations for multi-qubit systems. By using two entangled measures, namely the concurrence C and the negativity Nc, we establish tighter monogamy inequalities for their α-th power than those in all the existing ones. We also illustrate the tightness of our results for some classes of quantum states.
TL;DR: The merits of Nelson's concurring opinion in the Dred Scott case of 1857 have not been adequately recognized as discussed by the authors , and it is worth noting that Nelson took ground that was legally more secure at the time than did either Chief Justice Taney, in his opinion for the Court, or the dissenters, Justices McLean and Curtis.
Abstract:
The merits, comparative and absolute, of Justice Samuel Nelson’s concurring opinion in the Dred Scott case of 1857 have not been adequately recognized. Nelson took ground that was legally more secure at the time than did either Chief Justice Taney, in his opinion for the Court, or the dissenters, Justices McLean and Curtis. Refusing to follow Taney’s ill-supported denials of Black citizenship and Congressional power over the Territories, he also understood better than the dissenters what conflict-of-laws doctrine, the precedent of Swift v. Tyson (1842), and the law of marriage and divorce implied for Scott. Nelson’s opinion carried a mix of political implications, but it possessed more credibility than the other opinions in the case for its solid grounding in accepted legal principles and freedom from overt partisanship.
TL;DR: In this paper , the authors investigated the relation between the amount of entanglement localized on a chosen subsystem of a multiqubit system via local measurements on the rest of the system, and the bipartite entenglement that is lost during this measurement process.
Abstract: We investigate the relation between the amount of entanglement localized on a chosen subsystem of a multiqubit system via local measurements on the rest of the system, and the bipartite entanglement that is lost during this measurement process. We study a number of paradigmatic pure states, including the generalized Greenberger--Horne--Zeilinger (GHZ), the generalized $W$ (gW), Dicke, and the generalized Dicke states. For the generalized GHZ and $W$ states, we analytically derive bounds on localizable entanglement in terms of the entanglement present in the system prior to the measurement. Also, for the Dicke and the generalized Dicke states, we demonstrate that with increasing system size, localizable entanglement tends to be equal to the bipartite entanglement present in the system over a specific partition before measurement. We extend the investigation numerically in the case of arbitrary multiqubit pure states. We also analytically determine the modification of these results, including the proposed bounds, in situations where these pure states are subjected to single-qubit phase-flip noise on all qubits. Additionally, we study one-dimensional paradigmatic quantum spin models, namely, the transverse-field XY model and the XXZ model in an external field, and numerically demonstrate a cubic dependence of the localized entanglement on the lost entanglement. We show that this relation is robust even in the presence of disorder in the strength of the external field.
TL;DR: In this paper , a deterministic entanglement transmission (DET) scheme was proposed to improve the performance of the classical CEP scheme in a large-scale quantum network.
Abstract: The performance of distributing entanglement between two distant nodes in a large-scale quantum network (QN) of partially entangled bipartite pure states is generally benchmarked against the classical entanglement percolation (CEP) scheme. Improvements beyond CEP were only achieved by nonscalable strategies for restricted QN topologies. This paper explores and amplifies a new and more effective mapping of a QN, referred to as concurrence percolation theory (ConPT), that suggests using deterministic rather than probabilistic protocols for scalably improving on CEP across arbitrary QN topology. More precisely, we implement ConPT via a deterministic entanglement transmission (DET) scheme that is fully analogous to resistor network analysis, with the corresponding series and parallel rules represented by deterministic entanglement swapping and concentration protocols, respectively. The main contribution of this paper is to establish a powerful mathematical framework, which is applicable to arbitrary $d$-dimensional information carriers (qudits), that provides different natural optimality metrics in terms of generalized $k$-concurrences (a family of fundamental entanglement measures) for different QN topologies. In particular, we conclude that the introduced DET scheme (a) is optimal over the well-known nested repeater protocol for distilling entanglement from partially entangled qubits and (b) leads to higher success probabilities of obtaining a maximally entangled state than using CEP. The implementation of the DET scheme is experimentally feasible as tested on IBM's quantum computation platform.
TL;DR: In this article , an analytical inquisition of photonic entanglement generation circuit (PEGC) for non-local qubits designed using quantum dot within the optical micro-cavity, considering the realistic environment, is presented.
Abstract: This paper presents the analytical inquisition of photonic entanglement generation circuit (PEGC) for non-local qubits designed using quantum dot within the optical micro-cavity, considering the realistic environment. It is established that the concurrence of the PEGC is considerably contingent on the interplay between the spin of quantum dot and photon within the optical micro-cavity. The maximum concurrence obtained is 0.6124 at normalized coupling strength (g/k) = 0.3 and normalized side leakage rate (ks/k) = 0.1 and 0.9011 at g/k = 4 and ks/k = 0.1 with and without a noisy environment, respectively. Different quantum cryptography-based protocols may be implemented using reported work.
06 Jun 2023
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06 Apr 2023
TL;DR: In this article , the authors examine the law of treaties in the jurisprudence of the ICJ and highlight the Court's position on key selected issues of interpretation: specifically the language of the treaty, time and treaty interpretation; and the role of policy.
Abstract: This chapter examines the law of treaties in the jurisprudence of the ICJ. The author highlights the Court’s position on key selected issues of interpretation: specifically the language of the treaty; time and treaty interpretation; and the role of policy. The chapter also considers issues of systemic integration, hierarchy and concurrence of rules.
17 May 2023
TL;DR: In this paper , the authors considered an entanglement swapping protocol in three successive stages to produce the distributed entangled state of superconducting (SC) qubits, where the external magnetic fields on capacitively coupled pairs (2, 3) and (6, 7) are implemented for modulating the qubits.
Abstract: Abstract In recent decade the entangled state generation is of great importance in the quantum information processing and technologies. In this paper, producing the distributed entangled state of superconducting (SC) qubits is considered using an entanglement swapping protocol in three successive stages. The SC qubit pairs (i, i+1 with i=1, 3, 5, 7), where each pair of the qubits has been placed on a separate chip, are initially prepared in maximally entangled states. The external magnetic fields on capacitively coupled pairs (2, 3) and (6, 7) are implemented for modulating the qubits. Then, the SC qubits (1, 4) and (5, 8) are converted into entangled states via operating proper measurements instead of Bell state measurement (which is generally a hard task). Finally, the distributed entangled state of target SC qubits (1, 8) can be obtained by applying external magnetic fields on qubits (4, 5) and operating suitable measurements. This process is studied in the absence and presence of thermal decoherence effects. The concurrence, as a measure of entanglement between two qubits, success probability of the distributed entangled states and fidelity are evaluated, by which we find that the state of target SC qubits (1, 8) is converted to Bell state at some moments of time. Also, there exist appropriate conditions in which maximum of success probability of the obtained states in each stage approaches 1. Also, the maxima of concurrence and success probability gradually decrease due to thermal noise as time goes on. Moreover, convincing amounts of fidelity, success probability and entanglement can be obtained for the achieved entangled states.
01 Jan 2023
TL;DR: The concurrence est aujourd’hui au premier plan des régulations étatiques nationales ou européennes as discussed by the authors , and elle fait de nouveau l'objet d'un vif débat, en France comme ailleurs.
Abstract: La concurrence est aujourd’hui au premier plan des régulations étatiques nationales ou européennes. Mais elle fait de nouveau l’objet d’un vif débat, en France comme ailleurs : les politiques, les institutions et le droit qui la soutiennent doivent-ils avoir comme objectif exclusif le bien-être des consommatrices et consommateurs ? ou bien ont-ils à limiter les conséquences économiques et sociétales du pouvoir de marché des firmes privées comme publiques et des réseaux sur lesquelles elles...
TL;DR: In this paper , the authors proposed probabilistic entanglement swapping with different amounts of initial entanglements, and showed that the maximal entenglement in the measuring-basis is not required for attaining the EPR projection.
TL;DR: In this paper , two methods to achieve a probabilistic entanglement concentration for bipartite quantum systems with a large dimensionality for N = 1, regarding a reasonably good probability of success at the expense of having a non-maximal entenglement, were studied.
Abstract: Considering pure quantum states, entanglement concentration is the procedure where, from N copies of a partially entangled state, a single state with higher entanglement can be obtained. Obtaining a maximally entangled state is possible for N=1. However, the associated success probability can be extremely low when increasing the system’s dimensionality. In this work, we study two methods to achieve a probabilistic entanglement concentration for bipartite quantum systems with a large dimensionality for N=1, regarding a reasonably good probability of success at the expense of having a non-maximal entanglement. Firstly, we define an efficiency function Q considering a tradeoff between the amount of entanglement (quantified by the I-Concurrence) of the final state after the concentration procedure and its success probability, which leads to solving a quadratic optimization problem. We found an analytical solution, ensuring that an optimal scheme for entanglement concentration can always be found in terms of Q. Finally, a second method was explored, which is based on fixing the success probability and searching for the maximum amount of entanglement attainable. Both ways resemble the Procrustean method applied to a subset of the most significant Schmidt coefficients but obtaining non-maximally entangled states.
TL;DR: In this paper , the authors propose a method to solve the problem of "not available" data: https://www.youtube.com/watch/watch?feature=youtu.
Abstract: Not available.
TL;DR: In this article , the authors investigated the nonlinear interaction between a three-level Ξ-type atom and a bimodal field and obtained the general solution by using the Schrődinger equation when the atom and the field are initially prepared in the excited state and coherent state, respectively.
Abstract: We investigate some new aspects of the nonlinear interaction between a three-level Ξ-type atom and bimodal field. The photon-assisted atomic phase damping, detuning parameter, Kerr nonlinearity and the time-dependent coupling have been considered. The general solution has been obtained by using the Schrődinger equation when the atom and the field are initially prepared in the excited state and coherent state, respectively. The atomic population inversion and concurrence are discussed. It is shown that the time-dependent coupling parameter and the detuning parameter can be considered as quantum controller parameters of the atomic population inversion and quantum entanglement in the considered model.