Phenomenon Of Entanglement Sudden Death Research Articles

Gaussian quantum entanglement in curved spacetime

The influence of Hawking radiation on quantum entanglement for bimodal Gaussian states near a Schwarzschild black hole is investigated. It is shown that for a thermal squeezed state of a bimodal bosonic system the Hawking radiation reduces and even can destroy the entanglement between the mode of a Kruskal observer Alice and the mode of Bob, who is an accelerated observer hovering outside the event horizon of black hole. By contrary, the Hawking radiation increases and even can generate quantum entanglement between Bob and anti-Bob, who is a hypothetical observer inside event horizon. We show that in both these scenarios the competition between the contrary influences produced by Hawking temperature, squeezing and field frequency, may favour the preservation of the quantum entanglement. We investigate also the influence of the thermal environment on the behaviour in time of the entanglement between the considered observers and show that the entanglement is destroyed in a finite time for both considered bipartite scenarios of observers Alice and Bob, and respectively Bob and anti-Bob, for non-zero values of the temperature of the thermal environment, i.e. the phenomenon of entanglement sudden death takes place. For a zero temperature of the thermal bath the initial existing entanglement is decreasing over time, but it keeps for all finite times a non-zero value and the logarithmic negativity tends to zero only in the limit of infinite time.

The dynamic of quantum entanglement of two dimensional harmonic oscillator in non-commutative space

In the present paper, we study the influence of non-commutativity on entanglement in a system of two oscillators-modes in interaction with its environment. The considered system is a two-dimensional harmonic oscillator in non-commuting spatial coordinates coupled to its environment. The dynamics of the covariance matrix, the separability criteria for two Gaussian states in non-commutative space coordinates, and the logarithmic negativity are used to evaluate the quantum entanglement in the system, which is compared to the commutative space coordinates case. The result is applied for two initially entangled states, namely the squeezed vacuum and squeezed thermal states. It can be observed that the phenomenon of entanglement sudden death appears more early in the system for the case of squeezed vacuum state than in the case of squeezed thermal state. Thereafter, it is also observed that non-commutativity effects lead to an increasing of entanglement of initially entangled quantum states, and reduce the separability in the open quantum system. It turns out that a separable state in the usual commutative quantum mechanics might be entangled in non-commutative extension.

Dynamics of quantum correlations under intrinsic decoherence in a Heisenberg spin chain model with Dzyaloshinskii–Moriya interaction

By taking into account the effect of intrinsic decoherence and by using Milburn’s dynamical master equation, we study the temporal evolution of quantum correlations in a two-qubit XXZ Heisenberg spin chain model with Dzyaloshinskii–Moriya (DM) interaction and an external nonuniform magnetic field both directed along the z-axis. We use the concurrence (C) to detect entanglement and the local quantum uncertainty (LQU) to measure discord-like correlations. We consider three cases of initial quantum states: the mixed state, the Werner state and the pure state. For the mixed initial state and the Werner initial state, our results show that the external magnetic field strongly stimulates the effect of intrinsic decoherence which can highlight the entanglement sudden death phenomenon, while the LQU is resistant to sudden death. In addition, the DM interaction makes the effect of intrinsic decoherence more pronounced. However, a weak DM interaction can markedly improve quantum correlations and thus cause the phenomenon of entanglement sudden revival. On the other hand, and especially for the initial “uncorrelated” state (in terms of entanglement and LQU) with a zero nonuniform magnetic field and no DM interaction, it is easier to generate a strong entanglement, but it is difficult to generate LQU. Finally, we have found that when the system is initially “uncorrelated,” the nonuniform magnetic field can make the system strongly correlated for very remarkable steady-state values (in particular entanglement). Other results will also be discussed.

Plasmonic-modulated dissipative-driven multiqubit entanglement under asymmetric detuning

A dissipative-driven system can generate steady-state entanglement robust to control parameters, while a quantum plasmonic system has the advantages of being strongly coupled to qubits and manipulation of electromagnetic waves in the subwavelength regime. We propose an effective multiqubit dissipative-driven entanglement model for a plasmonic system which takes into account coupling of the plasmonic cavity and qubits as well as the direct coupling between any two qubits and develop a numerical solution of the effective model on a scalable composite plasmonic structure. In this structure, the multiqubit entanglement under asymmetric detuning, especially for those combinations containing pairs of antisymmetric detuning qubits, achieves stronger steady-state entanglement measured by negativity and pairwise concurrence. The robustness of multiqubit entanglement against variations of the control parameters is also presented. In addition, the phenomenon of entanglement sudden death caused by the driving field in entanglement dynamics is investigated. Our model shows evidence that quantum plasmonics has great potential in multiqubit entanglement.

Nonlocal quantum correlations under amplitude damping decoherence

Different nonlocal quantum correlations of entanglement, steering and Bell nonlocality are defined with the help of local hidden state (LHS) and local hidden variable (LHV) models. Considering their unique roles in quantum information processing, it is of importance to understand the individual nonlocal quantum correlation as well as their relationship. Here, we investigate the effects of amplitude damping decoherence on different nonlocal quantum correlations. In particular, we have theoretically and experimentally shown that the entanglement sudden death phenomenon is distinct from those of steering and Bell nonlocality. In our scenario, we found that all the initial states present sudden death of steering and Bell nonlocality, while only some of the states show entanglement sudden death. These results suggest that the environmental effect can be different for different nonlocal quantum correlations, and thus, it provides distinct operational interpretations of different quantum correlations.

The entanglement dynamics of superposition of fermionic coherent states in Heisenberg spin chains

Employing the I-concurrence (Ic) measure, entanglement dynamics of superposition of isospin fermionic coherent states (SFCS) in Heisenberg spin chains of Ising, XX, XXX and XXZ models in the presence of Dzyaloshinskii–Moriya (DM) interaction and magnetic field is studied. For the above-mentioned models, the entanglement dynamics of SFCSs is independent of magnetic field effect and the DM interaction effect introduces the quantum fluctuations in the entanglement dynamics of the system. It is shown that depending on the choice of the models in the absence of DM interaction, entanglement dynamics alter by applying and increasing the magnetic field to the first (second) part of the system. We showed that by increasing the spin of the fermionic coherent states (j) and, consequently, increasing their dimension d = 2j + 1, the entanglement dynamics of the SFCS states sharply increases and fluctuates at a higher level. Our results indicate no entanglement sudden death phenomenon under the examined conditions.

Properties of Entanglement between the JC Model and Atom-Cavity-Optomechanical System

We investigate the dynamics of remote entanglement in the system consisting of a Jaynes-Cummings model and an atom-cavity-optomechanical system. Meanwhile, we find that the remote entanglement is related to the initial entanglement degree between two atoms, the coupling strength between atom and cavity. Moreover, the phenomenon of entanglement sudden death appears in the evolution of entanglement for some initial conditions. By investigating the entanglement transfer among two atoms and cavity 1, we show that the entanglement transfer can be realized at some special time. In particular, we evaluate the tripartite entanglement of the two atoms and cavity 1 through π-tangle, and prepare the larger tripartite entanglement. This implementation of tripartite entanglement might provide a potential way to realize improved information processing and distributed quantum computing.

Free and bound entanglement dynamics in qutrit systems under Markov and non-Markov classical noise

We investigate in detail the dynamics of decoherence, free and bound entanglements, and the conversion from one to another (quantum state transitions), in a two non-interacting qutrits system initially entangled and subject to independents or a common classical noise. Both Markovian and non-Markovian environments are considered. Furthermore, isotropic and bound entangled states for qutrits systems are considered as initial states. We show the efficiency of the formers over the latters against decoherence, and in preserving quantum entanglement. The loss of coherence increases monotonically with time up to a saturation value depending upon the initial state parameter and is stronger in a collective Markov environment. For the non-Markov regime the presence or absence of entanglement revival and entanglement sudden death phenomena is deduced depending on both the peculiar characteristics of the noise, the physical setup and the initial state of the system. We demonstrate distillability sudden death for conveniently selected parameters in bound entangled states; meanwhile, it is completely absent for isotropic states, where entanglement sudden death is avoided for dynamic noise independently of the noise regime and the physical setup. Our results indicate that distillability sudden death under the Markov/non-Markov noise considered can be avoided depending upon the physical setup.

Effects of cavity–cavity interaction on the entanglement dynamics of a generalized double Jaynes–Cummings model

We consider a generalized double Jaynes–Cummings model consisting of two isolated two-level atoms, each contained in a lossless cavity that interact with each other through a controlled photon-hopping mechanism. We analytically show that at low values of such a mediated cavity–cavity interaction, the temporal evolution of entanglement between the atoms, under the effects of cavity perturbation, exhibits the well-known phenomenon of entanglement sudden death (ESD). Interestingly, for moderately large interaction values, a complete preclusion of ESD is achieved, irrespective of its value in the initial atomic state. Our results provide a model to sustain entanglement between two atomic qubits, under the adverse effect of cavity induced perturbation, by introducing a non-intrusive inter-cavity photon exchange that can be physically realized through cavity-QED setups in contemporary experiments.

Entanglement and measurement-induced nonlocality of mixed maximally entangled states in multipartite dynamics

The maximally entangled state can be in a mixed state as well as the well-known pure state. Taking the negativity as a measure of entanglement, we study the entanglement dynamics of bipartite, mixed maximally entangled states (MMESs) in multipartite cavity-reservoir systems. It is found that the MMES can exhibit the phenomenon of entanglement sudden death, which is quite different from the asymptotic decay of the pure-Bell-state case. We also find that maximal entanglement cannot guarantee maximal nonlocality and the MMES does not correspond to the state with maximal measurement-induced nonlocality (MIN). In fact, the value and dynamic behavior of the MIN for the MMESs are dependent on the mixed state probability. In addition, we investigate the distributions of negativity and the MIN in a multipartite system, where the two types of correlations have different monogamous properties.

Dynamics of Entanglement in Qubit-Qutrit with x-Component of DM Interaction

In this present paper, we study the entanglement dynamics in qubit A-qutrit B pair under x component of Dzyaloshinshkii–Moriya interaction (Dx) by taking an auxiliary qubit C. Here, we consider an entangled qubit-qutrit pair initially prepared in two parameter qubit-qutrit states and one auxiliary qubit prepared in pure state interacts with the qutrit of the pair through DM interaction. We trace away the auxiliary qubit and calculate the reduced dynamics in qubit A-qutrit B pair to study the influence of the state of auxiliary qubit C and Dx on entanglement. We find that the state (probability amplitude) of auxiliary qubit does not influence the entanglement, only Dx influences the same. The phenomenon of entanglement sudden death (ESD) induced by Dx has also been observed. We also present the affected and unaffected two parameter qubit-qutrit states by Dx.

Dynamics of three-qubit systems in a noisy environment

Some properties of three-qubit systems interacting with a noisy environment are discussed. The amount of the survival entanglement is quantified for the Greenberger–Horne–Zeilinger (GHZ) and W states. It is shown that the entanglement decay depends on the noise type (correlated or non-correlated), the number of interacting qubits with the environment, and the initial state that passes through this noisy environment. In general, the GHZ state is more fragile than the W state. The phenomenon of entanglement sudden death appears in the GHZ state only for non-correlated noise.

Influence of Dzyaloshinshkii–Moriya interaction on quantum correlations in two-qubit Werner states and MEMS

In this paper, we study the influence of Dzyaloshinskii–Moriya (DM) interaction on quantum correlations in two-qubit Werner states and maximally entangled mixed states (MEMS). We consider our system as a closed system of a qubit pair and one auxiliary qubit, which interact with any one of the qubit of the pair through DM interaction. We show that DM interaction, taken along any direction (x or y or z), does not affect two-qubit Werner states. On the other hand, the MEMS are affected by x and z components of DM interaction and remain unaffected by the y component. Further, we find that the state (i.e., probability amplitude) of auxiliary qubit does not affect the quantum correlations in both the states, and only DM interaction strength influences the quantum correlations. So one can avoid the intention to prepare the specific state of auxiliary qubit to manipulate the quantum correlations in both the states. We mention here that avoiding the preparation of state can contribute to cost reduction in quantum information processing. We also observe the phenomenon of entanglement sudden death in the present study.

Entanglement Dynamics Between Two Atoms Within Different W-like Initial States

We investigate the entanglement dynamics between two atoms which are trapped in an optical cavity with the help of the concurrence and the negativity for two different kinds of normalized W-like initial states. The results show that one of them can suffer the so-called entanglement sudden death (ESD) depending on parameters of the initial state when the optical cavity in the vacuum state, while the other one does not for whatever parameters. However when the initial optical cavity photon number is nonzero, no matter what W-like state as atoms' initial state, the atoms' subsystem always undergoes the ESD phenomenon. Meanwhile, by comparing concurrence with negativity, we find that our model gives a concrete example to support the conclusions in the previous reference.

Dynamics of Entanglement in the Cavity with Nonlinear Medium

We investigate the evolution of initial entangled two-atom in cavity with single-mode light field. Using the method of negative eigenvalue of partially transposed matrix we analysis the evolution of the entanglement of the two-atom in a field of number state and Kerr-media environment and find that entanglement sudden death phenomenon occurs in the number of particles field. When the atoms interact with the Kerr medium, we obtain that the phenomenon of sudden death can be eliminated in the particle-number field, and the entanglement of two-atom oscillates around a high-value.

EFFECT OF MARKOV AND NON-MARKOV CLASSICAL NOISE ON ENTANGLEMENT DYNAMICS

We analyze the effect of a classical noise into the entanglement dynamics between two particles, initially entangled, subject to continuous time quantum walks in a one-dimensional lattice. The noise is modeled by randomizing the transition amplitudes from one site to another. Both Markovian and non-Markovian environments are considered. For the Markov regime an exponential decay of the initial quantum correlation is found, while the loss of coherence of the quantum state increases monotonically with time up to a saturation value depending upon the degrees of freedom of the system. For the non-Markov regime the presence or absence of entanglement revival and entanglement sudden death phenomena is found or deduced depending on the peculiar characteristics of the noise. Our results indicate that the entanglement dynamics in the non-Markovian regime is affected by the persistence of the memory effects of the environment and by its intrinsic features.

Entanglement evolution of three-qubit mixed states in multipartite cavity—reservoir systems

We analyze the multipartite entanglement evolution of three-qubit mixed states composed of a GHZ state and a W state. For a composite system consisting of three cavities interacting with independent reservoirs, it is shown that the entanglement evolution is restricted by a set of monogamy relations. Furthermore, as quantified by the negativity, the entanglement dynamical property of the mixed entangled state of cavity photons is investigated. It is found that the three cavity photons can exhibit the phenomenon of entanglement sudden death (ESD). However, compared with the evolution of a generalized three-qubit GHZ state which has the equal initial entanglement, the ESD time of mixed states is later than that of the pure state. Finally, we discuss the entanglement distribution in the multipartite system, and point out the intrinsic relation between the ESD of cavity photons and the entanglement sudden birth of reservoirs.

Controlling entanglement dynamics via Raman interaction in two-mode cavity QED

We investigate the entanglement dynamics of an entangled atom pair via Wootters' concurrence. Only one atom of the pair interacts with a two-mode cavity field via a Raman interaction. The number simulation shows that the entanglement of the atom pair will display sudden death and revival phenomena when the cavity photon numbers and the two-mode atom–cavity coupling strengths are changed. Due to the two-mode field effect, the entanglement sudden death phenomenon will disappear more easily by enlarging the different cavity mode–atom coupling ratio. The oscillation rate of the concurrence is enlarged by increasing the mean photon number of the cavity field.

Entanglement transfer via two arrays of coupled resonator waveguides

We propose a scheme for transferring entanglement through two independent arrays of coupled resonator waveguides, where a three-level atom is embedded in each resonator. We investigate the entanglement dynamics of the transferred state. The influence of initial states and applied lasers on the entanglement sudden death phenomenon is also discussed. Furthermore, we study the dynamics of pairwise quantum correlations measured by the quantum discord.

Sudden death and robustness of quantum correlations in the weak- or strong-coupling regime

We study the dynamics of quantum discord and entanglement of two entangled two-level atoms within two isolated and dissipative cavities in the weak- or strong-coupling regime. The quantum entanglement are measured by concurrence and relative entropy. The quantum discord of two atoms based on quantum mutual information and relative entropy are also calculated. In the weak-coupling regime, the sudden death of quantum discord and entanglement of two atoms can occur simultaneously within a short interaction time. When the interaction time is long, quantum discord and entanglement of two atoms could be partially preserved due to the long-lived nature of quantum discord and entanglement. However, in the strong-coupling regime, there is no sudden death of quantum discord though the entanglement sudden death phenomenon occurs. In addition, we observe that entanglement and discord will be destroyed eventually when the atom-field interactions are strong. We also address the issue of experimental realization briefly.