Quantum Correlations Reduce Classical Correlations with Ancillary Systems

We illustrate the dichotomy of classical/quantum correlations by virtue of monogamy. More precisely, we show that correlations in a bipartite state are classical if and only it each party ot the state can be perfectly correlated with other ancillary systems. In particular, this means that if there are quantum correlations between two parties, then the classical （as well as quantum） correlating capabilities of the two parties with other systems have to be strictly reduced.     

Propagation of Correlations in Quantum Lattice Systems

We provide a simple proof of the Lieb-Robinson bound and use it to prove the existence of the dynamics for interactions with polynomial decay. We then use our results to demonstrate that there is an upper bound on the rate at which correlations between observables with separated support can accumulate as a consequence of the dynamics.     

Relativistic Quantum Correlations Between Spin-1/2 Particles

It is shown that a fully relativistic formulation of spin measurements and correlations does not add any new feature to the standard analysis of Bell and the deduction of his inequality. It follows, therefore, that the motion of reference frames does not affect the correlations between spatially separated particles.     

Tighter Constraints of Quantum Correlations Among Multipartite Systems

International Journal of Theoretical Physics - We provide a characterization of multipartite systems constraints in terms of quantum correlations. By using the Hamming weight of the binary vectors...     

Quantum Correlations of Two Relativistic Spin-12 Particles Under Noisy Channels

We study the quantum correlation dynamics of bipartite spin-\(\frac {1}{2}\) density matrices for two particles under Wigner rotations induced by Lorentz transformations which is transmitted through noisy channels. We compare quantum entanglement, geometric discord(GD), and quantum discord (QD) for bipartite relativistic spin-\(\frac {1}{2}\) states under noisy channels. We find out QD and GD tend to death asymptotically but a sudden change in the decay rate of the entanglement occurs under noisy channels. Also, bipartite relativistic spin density matrices are considered as a quantum channel for teleportation one-qubit state under the influence of depolarizing noise and compare fidelity for various velocities of observers.     

Heat-to-Work Conversion by Exploiting Full or Partial Correlations of Quantum Particles

It is shown how information contained in the pairwise correlations (in general, partial) between atoms of a gas can be used to completely convert heat taken from a thermostat into mechanical work in a process of relaxation of the system to its thermal equilibrium state. Both classical correlations and quantum correlations (entanglement) are considered. The amount of heat converted into work is proportional to the entropy defect of the initial state of the system. For fully correlated particles, in the case of entanglement the amount of work obtained per particle is twice as large as in the case of classical correlations. However, in the case of entanglement, the amount of work does not depend on the degree of correlation, in contrast to the case of classical correlations. The results explicitly demonstrate the equivalence relation between information and work for the case of two-particle correlations.     

Quantum Correlations and Speed Limit of Central Spin Systems

In this article, single, and two-qubit central spin systems interacting with spin baths are considered and their dynamical properties are discussed. The cases of interacting and non-interacting spin baths are considered and the quantum speed limit (QSL) time of evolution is investigated. The impact of the size of the spin bath on the quantum speed limit for a single qubit central spin model is analyzed. The quantum correlations for (non-)interacting two central spin qubits are estimated and their dynamical behavior with that of QSL time under various conditions are compared. How QSL time could be availed to analyze the dynamics of quantum correlations is shown.     

Characterizing Quantum Correlations in Arbitrary-Dimensional Bipartite Systems Using Hurwitz's Theory

Quantum correlations play vital roles in the quantum features in quantum information processing tasks. Among the measures of quantum correlations, quantum discord （QD） and entanglement of formation （EOF） axe two significant ones. Recent research has shown that there exists a relation between QD and EOF, which makes QD more significant in quantum information theory. However, until now, there exists no general method of chaxaeterizing quantum discord in high-dimensional quantum systems. In this paper, we have proposed a general method for calculating quantum discord in axbitraxy-dimensionM bipaxtite quantum systems in terms of Hurwitz＇s theory. Applications including the Werner state, the spin-1 XXZ model thermal equilibrium state, the Horodecki state, and the separable-bound-free entanglement state are investigated. We present the method of obtaining the EOF of axbitraxy-dimensional bipaxtite quantum states via purification, and the relations.hip between QD and EOF.     

Enhancement of Quantum Correlations in Qubit-Qutrit Systems under the non-Markovian Environment

We investigate the time evolution of quantum correlations of a hybrid qubit-qutrit system under the classical Ornstein-Uhlenbeck(OU) noise. Here we consider two different one-parameter families of qubit-qutrit states which independently interact with the non-Markovian reservoirs. A comparison with the Markovian dynamics reveals that for the same set of initial condition parameters, the non-Markovian behavior of the environment plays an important role in the enhancement of the survival time of quantum correlations. In addition, it is observed that the non-Markovian strength(γ/Γ) has a positive impact on the correlations time. For the initial separable states it is found that there is a finite time interval in which the geometric quantum discord is frozen despite the presence of a noisy environment and that interval can be further prolonged by using the non-Markovian property. Moreover, its decay can be significantly delayed.     

On Quantum Systems of Particles with Singular Magnetic Interaction

Abstract

For systems of particles with singular magnetic interation for special choice of a selfadjoint extension of the Hamiltoniam equilibrium reduced density matrices are calculated in the thermodynamic limit for simplest pair magnetic potentials.     

Dynamics of Multi-Level Open Quantum Systems with Initial System-Environment Correlations

Physics of Particles and Nuclei Letters - Exact and approximate master equations were derived by the projection operator method for the reduced statistical operator of a multi-level open quantum...     

Quantum Correlations Evolution Asymmetry in Quantum Channels

It was demonstrated that the entanglement evolution of a specially designed quantum state in the bistochastic channel is asymmetric. In this work, we generalize the study of the quantum correlations, including entanglement and quantum discord, evolution asymmetry to various quantum channels. We found that the asymmetry of entanglement and quantum discord only occurs in some special quantum channels, and the behavior of the entanglement evolution may be quite different from the behavior of the quantum discord evolution. To quantum entanglement, in some channels it decreases monotonously with the increase of the quantum channel intensity. In some other channels, when we increase the intensity of the quantum channel, it decreases at first, then keeps zero for some time, and then rises up. To quantum discord, the evolution becomes more complex and you may find that it evolutes unsmoothly at some points. These results illustrate the strong dependence of the quantum correlations evolution on the property of the quantum channels.     

Asymptotic Correlations in Gapped and Critical Topological Phases of 1D Quantum Systems

Journal of Statistical Physics - Topological phases protected by symmetry can occur in gapped and—surprisingly—in critical systems. We consider non-interacting fermions in one dimension...     

Quantum Correlations in Werner Derivatives

Quantum correlations in Werner derivatives are studied with two different approaches, i.e., measurement-induced disturbance (MID) [Phys. Rev. A 77 (2008) 022301] and ameliorated MID (AMID) [J. Phys. A 44 (2011) 352002]. They are derived via strict deductions with MID while numerically calculated via the measurement optimization with AMID. Interestingly, quantum correlations captured with both approaches are completely coincident. Moreover, some distinct features of the quantum correlations and their underlying physics are exposed via analyses and discussions.     

Quantum Correlations in Werner Derivatives

Quantum correlations in Werner derivatives are studied with two diferent approaches,i.e.,measurementinduced disturbance(MID)[Phys.Rev.A 77(2008)022301]and ameliorated MID(AMID)[J.Phys.A 44(2011)352002].They are derived via strict deductions with MID while numerically calculated via the measurement optimization with AMID.Interestingly,quantum correlations captured with both approaches are completely coincident.Moreover,some distinct features of the quantum correlations and their underlying physics are exposed via analyses and discussions.     

量子能谱中的长程关联

从可积系统求迹公式出发,运用Einstein-Brillouin-Keller(EBK)量子化条件,导出了二维无关联振子系统周期轨道作用量量子化条件,由此发现了量子能级与周期轨道之间的对应关系.这种对应关系表明,如果两条能级对应的周期轨道的拓扑相同,这两条能级对回归函数的贡献相干.回归谱中的一个峰是量子能谱中一组与具有相同拓扑的周期轨道相对应的能级之间相干的结果,这一组能级间存在着长程关联.     

The Dynamical Evolution of Quantum Correlations in the Two Isolate Spin Particles Coupled to a Common Bath

We study the dynamical evolution of quantum correlations between two central spins independently coupled to a common bath, which are represented by quantum entanglement and quantum discord. According to the results of the exact solution, we show that quantum discord is more robust and includes richer correlation than quantum entanglement due to the nonvanishing quantum correlation in the region of entanglement death, i.e., the separable states maybe contain nonclassical correlations. We discuss the effects of the intrinsic properties of the bath on quantum correlation between the two central spins in the XY and XXZ model baths. At the low temperature, the central system can keep the good quantum correlation. With the more spin number in the bath, the dynamical evolution of quantum correlation can be bounded with the small oscillation and finally approaches a stable value. In addition, we find that the interaction between the central spins and the bath in the z direction has the significant effects on quantum correlation of the central spin system.     

Dynamics of Super Quantum Correlations and Quantum Correlations for a System of Three Qubits

The dynamics of quantum discord for two qubits independently interacting with dephasing reservoirs have been studied recently.The authors [Phys.Rev.A 88(2013) 034304] found that for some Bell-diagonal states(BDS)which interact with their environments the calculation of quantum discord could experience a sudden transition in its dynamics,this phenomenon is known as the sudden change.Here in the present paper,we analyze the dynamics of normal quantum discord and super quantum discord for tripartite Bell-diagonal states independently interacting with dephasing reservoirs.Then,we find that basis change does not necessary mean sudden change of quantum correlations.