二体四维量子系统的广义concurrence

将Wootters的concurrence推广到了二体四维情形.作为一个解析的实例,计算了一类二体四维对称态的广义concurrence.

Mathematica在计算concurrence中的应用

利用Mathematica计算量子信息领域中的concurrence的一个程序，可以大大减少计算工作量。

Channel＇s Concurrence and Quantum Teleportation

Concurrence can measure the entanglement property of a system. If the channel is a pure state, positive concurrence state can afford the good performance in the teleportation process. If the channel ia a mixed state, positive concurrence state cannot assure the good performance in the teleportation. The conditions of the positive concurrence and the quantum teleportation in the Heisenberg spin ring is derived.

Concurrence of Quantum States: Algebraic Dynamical Method Study XXX Models in a Time-Depending Random External Field

Based on algebraic dynamics and the concept of the concurrence of the entanglement, we investigate the evolutive properties of the two-qubit entanglement that formed by Heisenberg XXX models under a time-depending external field. For this system, the property of the concurrence that is only dependent on the coupling constant J and total values of the external field is proved. Furthermore, we found that the thermal concurrence of the system under a static random external field is a function of the coupling constant J, temperature T, and the magnitude of external field.

Simple Scheme for Directly Measuring Concurrence of Two-Qubit Pure States in One Step

In the present work, a simple scheme for the direct measurement of the concurrence of two-qubit pure states is proposed. The scheme is based on trapped ions and only needs one step when the two identical pure states are given. The vibrational mode in our proposal is only virtually excited, which is important in view of decoherence.Furthermore, the scheme is feasible based on current technologies.

Direct measurement of the concurrence of hybrid entangled state based on parity check measurements

The hybrid entangled state is widely discussed in quantum information processing. In this paper, we propose the first protocol to directly measure the concurrence of the hybrid entangled state. To complete the measurement, we design parity check measurements(PCMs) for both the single polarization qubit and the coherent state. In this protocol, we perform three rounds of PCMs. The results show that we can convert the concurrence into the success probability of picking up the correct states from the initial entangled states. This protocol only uses polarization beam splitters, beam splitters, and weak cross-Kerr nonlinearities, which is feasible for future experiments. This protocol may be useful in future quantum information processing.

Eigenfunctions of Five-Qubit XX Chain and Ground State Concurrence

Use Jordan-Wigner transformation the eigenstates and eigenenergies of live qubits XX chain including external magnetic field are obtained. The concurrences Co,1 and Co,2 of ground state are obtained. For the ferromagnetic, when [（√5 - 1）/2]｜J｜ 〈 B ≤ ｜J｜, the values of C0,1 and C0,2 are the same. The C0,2 is easily broken by temperature.

Concurrence,tangle and fully entangled fraction

We show that although we cannot distil a singlet frora many pairs of bound entangled states, the concurrence and the tangle of two entangled quantum states are always strictly larger than those of one of them, even both entangled quantum states are bound entangled. We present a relation between the concurrence and the fidelity of optimal teleportation. We also give new upper and lower bounds for concurrence and tangle.

Study of Concurrence and D-Concurrence on Two-Qubits Resulted in Pair Coherent States in Language of SU(2) Coherent States

Pair coherent state, is a state of a two-mode radiation field that is known as a state with non-gaussian wave function. In this paper, study on the pair coherent state, we notice that with superposition of two first terms of this states, one two-qubits formed. Because of the importance of two-qubits in theory of quantum entanglement, with two different measures with the title of concurrence and D-concurrence, we have studied the amount of entanglement and discussed its details. At the end, we describe these measures for pair coherent states as a function of the amplitude of the SU（2） coherent states.

Randomly Generating Four Mixed Bell-Diagonal States with a Concurrences Sum to Unity

A two-qubit system in quantum information theory is the simplest bipartite quantum system and its concurrence for pure and mixed states is well known.As a subset of two-qubit systems,Bell-diagonal states can be depicted by a very simple geometrical representation of a tetrahedron with sides of length 2√2.Based on this geometric representation,we propose a simple approach to randomly generate four mixed Bell decomposable states in which the sum of their concurrence is equal to one.

Application of quantum algorithms to direct measurement of concurrence of a two-qubit pure state

This paper proposes a method to measure directly the concurrence of an arbitrary two-qubit pure state based on a generalized Grover quantum iteration algorithm and a phase estimation algorithm. The concurrence can be calculated by applying quantum algorithms to two available copies of the bipartite system, and a final measurement on the auxiliary working qubits gives a better estimation of the concurrence. This method opens new prospects of entanglement measure by the application of quantum algorithms. The implementation of the protocol would be an important step toward quantum information processing and more complex entanglement measure of the finite-dimensional quantum system with an arbitrary number of qubits.

A Probability Measure for Entanglement of Pure Two-Qubit Systems and a Useful Interpretation for Concurrence

A new probability measure for the quantification of entanglement of pure states is introduced.Numerical computations indicate that the derived measure is equal to concurrence,up to the precision of the computer program used.Hence it also provides a physical interpretation for concurrence.

Mutual Restriction between Concurrence and Intrinsic Concurrence for Arbitrary Two-Qubit States

Concurrence is viewed as the most commonly approach for quantifying entanglement of two-qubit states,while intrinsic concurrence contains concurrence of four pure states consisting of a special pure state ensemble concerning an arbitrary two-qubit state.Thus,a natural question arises:Whether there is a specified relation between them.We firstly examine the relation between concurrence and intrinsic concurrence for the maximally nonlocal mixed state under a special unitary operation,which is not yet rigorously proved.In order to obtain a general result,we investigate the relation between concurrence and intrinsic concurrence using randomly generated two-qubit states,and derive an inequality relation between them.Finally,we take into account the relation between concurrence and intrinsic concurrence in open systems,and reveal the ratio of the two quantum resources,which is only correlated with the experiencing channels.

A Comparison of the Concurrence and the Quantum Discord in a Two-Qubit System

The quantum correlation dynamics in an anisotropic Heisenberg XY Z model under decoherence are investigated with the use of concurrence C and quantum discord （QD）. There is a remarkable difference between the time evolution behaviors of these two correlation measures： there is a entanglement-sudden-death phenomenon in the concurrence while there is none in QD, which is valid for all of the initial states of this system, and the interval time of the entanglement death is found to be strongly dependent on the initial states and the parameters B and △. With the long-time limit the steady entanglement （SC） and steady quantum discord （SO, D） can be obtained. The magnitudes of SC and SQD are closely related to the parameters B and △, while the strength of the Dzyaloshinskii-Moriya interaction, D, has no influence. In addition, the effects of the parameters B and △ on SC and SQD display such different and complicated features that one cannot obtain a uniform law about them, thus we give an analytical explanation of this phenomenon. Lastly, it can be noted that the value of SC is not always larger than SQD, which is strongly dependent on the parameters B and △.

A Surfing Concurrence Transaction Model for Key-Value NoSQL Databases

As more and more application systems related to big data were developed, NoSQL (Not Only SQL) database systems are becoming more and more popular. In order to add transaction features for some NoSQL database systems, many scholars have tried different techniques. Unfortunately, there is a lack of research on Redis’s transaction in the existing literatures. This paper proposes a transaction model for key-value NoSQL databases including Redis to make possible allowing users to access data in the ACID (Atomicity, Consistency, Isolation and Durability) way, and this model is vividly called the surfing concurrence transaction model. The architecture, important features and implementation principle are described in detail. The key algorithms also were given in the form of pseudo program code, and the performance also was evaluated. With the proposed model, the transactions of Key-Value NoSQL databases can be performed in a lock free and MVCC (Multi-Version Concurrency Control) free manner. This is the result of further research on the related topic, which fills the gap ignored by relevant scholars in this field to make a little contribution to the further development of NoSQL technology.

Concurrence and Turnout Effect of Reforms on Electoral Processes in Mexico

Since the 1990s, the turnout in electoral processes has decreased, taking into account the Mexican context with its democratic transition, this decrease started after the 1994 federal election. The drop in turnout in federal elections had its lowest figure during the midterm elections of 2003, it picked up during the electoral process of 2009 and kept the same level of 2012. The change in the electoral turnout pattern for the federal elections in Mexico after 2009 can be explained as the combined effect of the electoral cycle and the concurrence between federal and local elections. Beginning from the hypothesis that there is a close link between institutions and contexts, the purpose of this study is to prove with the analysis of the electoral processes from 1997 to 2012, the effect of the electoral reforms--specifically the one in Article 116 of the Constitution in 2007-on turnout for federal elections of 2009 and 2012.

二非正交纯态相混合的concurrence

导出了两量子比特中二非正交纯态相混合的concurrence的明显表达式,并作了验证.推算表明,正交情形下的concurrence公式可以直接推广到非正交的情形.讨论了两纯态相混合的最大纠缠混合态和一些重要特殊情形.

Anthropogenic Influence on Decadal Changes in Concurrent Hot and Dry Events over China around the Mid-1990s

The frequency and duration of observed concurrent hot and dry events(HDEs) over China during the growing season(April–September) exhibit significant decadal changes across the mid-1990s. These changes are characterized by increases in HDE frequency and duration over most of China, with relatively large increases over southeastern China(SEC), northern China(NC), and northeastern China(NEC). The frequency of HDEs averaged over China in the present day(PD,1994–2011) is double that in the early period(EP, 1964–81);the duration of HDEs increases by 60%. Climate experiments with the Met Office Unified Model(MetUM-GOML2) are used to estimate the contributions of anthropogenic forcing to HDE decadal changes over China. Anthropogenic forcing changes can explain 60%–70% of the observed decadal changes,suggesting an important anthropogenic influence on HDE changes over China across the mid-1990s. Single-forcing experiments indicate that the increase in greenhouse gas(GHG) concentrations dominates the simulated decadal changes,increasing the frequency and duration of HDEs throughout China. The change in anthropogenic aerosol(AA) emissions significantly decreases the frequency and duration of HDEs over SEC and NC, but the magnitude of the decrease is much smaller than the increase induced by GHGs. The changes in HDEs in response to anthropogenic forcing are mainly due to the response of climatological mean surface air temperatures. The contributions from changes in variability and changes in climatological mean soil moisture and evapotranspiration are relatively small. The physical processes associated with the response of HDEs to GHG and AA changes are also revealed.

Clinical evidence in concurrence of retinitis pigmentosa and glaucoma

Glaucoma is rarely complicated by retinitis pigmentosa （RP）. To provide clinical evidences for this rare situation, we report the concurrence of these two diseases in two children of a Chinese family. In the present two-child Chinese family without positive history, the older sister presented with bilateral sector RP and coexisting chronic angle-closure glaucoma,and the brother with bilateral whole RP but without coexisting glaucoma. Clinical evidences in concurrence of variants of RP and glaucoma because of possible different gene mutations from the same genetic background represent a rare situation, which may provide clues for future researches in molecular pathogenesis of these rare diseases.

Lower Bound of Concurrence Based on Generalized Positive Maps

We study the concurrence of arbitrary dimensional bipartite quantum systems. By using a positive but not completely positive map, we present an anaJytical lower bound of concurrence. Detailed examples are used to show that our bound can detect entanglement better and can improve the well known existing lower bounds.