Dynamics Of Quantum Entanglement Research Articles

Tripartite Entanglement for Three-Qubit System in the Generalized Coleman-Hepp Model

Based on the solvable dynamical model for quantum measurement process, we consider three uncoupled particles interacting with their local one-dimensional (1D) spin arrays. Here the 1D spin arrays can be regarded as the local phase decoherence environments for the particles. To demonstrate the dynamics of quantum entanglement among three particles in measuring process, the tripartite negativity is introduced. Our study indicates that the tripartite negativity is determined jointly by the initial states and the dephasing factors for four kinds of initial states, including GHZ-type states, W-type states, Weiner-GHZ states, and Weiner-W states. We find the particle-spin array interaction can destroy the tripartite negativity, and the tripartite negativity is the same for the family of entangled GHZ states or the family of entangled W states. Furthermore, there exists the sudden death of tripartite negativity when the initial states are Weiner-GHZ states or Weiner-W states.

Action in Hamiltonian Models Constructed by Yang-Baxter Equation: Entanglement and Measures of Correlation

By using the quantum Yang-Baxterization approach, we investigate the dynamics of quantum entanglement under the actions of different Hamiltonians on the different two-qubit input states and analyze the effects of the Yang-Baxter operations on it. During any quantum process that takes place in a noisy environment, quantum correlations display behavior that does not increase. We point out that for two-qubit systems subject to actions of different Yang-Baxter operations the loss of correlations can be mitigated by the appropriate choice of the initial states and the Yang-Baxterization process. We show that in a noisy environment it possible to create the optimal conditions for performing any quantum information task.

Dynamics of quantum entanglement in matter field models

A review of the linear canonical transformations and its unitary representation is presented and its importance in the mathematical generation of a special two photon coherent state of light is demonstrated. The dynamical behaviour of the entanglement of the matter and field sectors of an initial composite system under the action of two effective model Hamiltonians is shown. The quantumness and delocalization properties of the corresponding electromagnetic field sectors are established. Finally for the two-photon process interacting with a two-level system, the violation of the Cauchy-Schwarz inequality is exhibited.

Probing topological states through the exact non-Markovian decoherence dynamics of a spin coupled to a spin bath in the real-time domain

In this paper, we explore the decoherence dynamics of a probing spin coupled to a spin bath, where the spin bath is given by a controllable 1D transverse-field Ising chain. The 1D transverse-field Ising chain with free-ends boundary condition is equivalent to a modified Kitaev model with non-local Majorana bound states in its topological phase. We find that the probing spin non-Markovian decoherence dynamics can manifest the topological structure of the spin chain. By controlling the external magnetic field on the Ising chain, we find the close relationships between the quantum phase transitions, the topological edge states, and the non-Markovian dynamics in real-time domain. We also investigate the corresponding quantum entanglement dynamics in this topological system.

Quantum information transfer and entangled state generation using superconducting qubits in the absence and presence of dissipation

In this paper, we propose a scheme for quantum information transfer by a gap-tunable bridge qubit between two superconducting (SC) qubits, which are initially prepared in separable quantum states. As is observed, enough high-fidelity and maximally entanglement between the two superconducting resonators, as well as between the two of qubits, can be achieved. It is shown that by implementing driven magnetic field to high detuned superconducting qubits, we are able to induce sidebands in the qubit–resonator and also qubit–qubit couplings. The influence of decay rates of qubits and resonator modes on the dynamics of quantum fidelity and entanglement is also investigated, either individually or simultaneously, by numerical analysis. Our numerical results show that the decay rate parameters have destructive, constructive, and no critical effect on the fidelity, depending on the chosen decay parameters. Moreover, they have destructive effects on the generated entangled state in the outlined quantum information transfer process.

Dynamics of quantum coherence and entanglement in an intrinsic noise model of a V-type qutrit system interacting with a coherent field

An analytical solution of the dynamical evolution of an intrinsic noise model of a V-type three-level atom confined in a cavity having one-mode coherent field via multi-photon transitions is obtained. We investigate the effect of the physical parameters of the qutrit-cavity unitary interaction, the intrinsic noise and the photon multiplicity, on important quantum effects such as: the atomic inversion, the quantum coherence, the entanglement and the total correlation. These physical parameters control the phenomenon of the collapses and revivals, and the regularity of the oscillatory behavior of the atomic-inversion. When the intrinsic noise is considered, the dynamics of the entropy, the negativity and the mutual information are different, while the entropy grows, the entanglement negativity and the mutual information degrades to their stationary values. It is found that the quantum coherence, the entanglement, the total correlation and their stationary values are very sensitive to any change in the physical parameters.

Entanglement Dynamics of a Two-qubit XYZ Spin Chain Under both Dzyaloshinskii-Moriya Interaction and Time-dependent Anisotropic Magnetic Field

In the present paper, the quantum entanglement dynamics of two qubits Heisenberg-XYZ spin chain under a time dependent magnetic field effects, and considering the Dzyaloshinskii-Moriya (DM) interactions is studied. Assuming the system as being influenced by a non-Markovian environment, the dynamics of entanglement through the concurrence is studied. It follows from the simulations that the time dependency character of the DM coupling, the external magnetic field, and the Heisenberg spin-spin coupling preserves longer entanglement in the system compared to the case with these parameters constant. Moreover, it also follows that the effects of the environment on the system induces the loss of entanglement and then, the time interval of entanglement sudden death highly depends on the initial state considered. It is also observed that by tuning the strength of the DM coupling associated with a time varying magnetic field and a time varying spin-spin anisotropic coupling, the system can be better protected from unwanted effects of the environment and thus, entanglement can be preserved for a longer period of time.

Quantum Fisher Information of Two Moving Four-Level Atoms

We investigate dynamics of quantum entanglement (QE) and quantum Fisher information (QFI) of a system of two four-level atoms moving in the thermal environment. The time evolution of the state vector of the whole quantum system interacting with the thermal field is investigated numerically in the presence of intrinsic decoherence (ID). We see that ID and the thermal environment play a prominent role in the time evolution of the quantum system. QFI and von Neumann entropy (VNE) show the opposite response during their time evolution in the presence of the thermal environment. QFI is seen as more prone to intrinsic decoherence when compared with the VNE in the presence of the thermal environment. VNE changes remarkably with increase in the intrinsic decoherence parameter without the atomic motion. However, the periodic response of VNE is seen because of the atomic motion which gets modest under environmental effects. The decay of VNE is further damped at larger time scales that confirm that ID affects the system dynamics in a thermal environment. Moreover, VNE and QFI saturate to a lower level for larger time-scales under these environments. The damping response of VNE is observed under intrinsic decoherence for larger time scales. The VNE and QFI saturate to a lower level for larger time scales under the environmental effects. Moreover, one sees that the thermal environment induces a quicker decay of VNE when compared with the decay induced by ID. In this manner, the ID and thermal environment are found to suppress the nonclassical effects of the quantum system.

Quantum entanglement dynamics based on composite quantum collision model**Project supported by the National Natural Science Foundation of China (Grant Nos. 61675115 and 11974209), the Taishan Scholar Project of Shandong Province of China (Grant No. tsqn201812059), and the Shandong Provincial Natural Science Foundation of China (Grant No. ZR2016JL005).

By means of composite quantum collision models, we study the entanglement dynamics of a bipartite system, i.e., two qubits S1 and S2 interacting directly with an intermediate auxiliary qubit SA, while SA is in turn coupled to a thermal reservoir. We are concerned with how the intracollisions of the reservoir qubits influence the entanglement dynamics. We show that even if the system is initially in the separated state, their entanglement can be generated due to the interaction between the qubits. In the long-time limit, the steady-state entanglement can be generated depending on the initial state of S1 and S2 and the environment temperature. We also study the dynamics of tripartite entanglement of the three qubits S1, S2, and SA when they are initially prepared in the GHZ state and separated state, respectively. For the GHZ initial state, the tripartite entanglement can be maintained for a long time when the collision strength between the environment qubits is sufficiently large.

Quantum coherence and correlation dynamics of two-qubit system in spin bath environment**Project supported by the National Natural Science Foundation of China (Grant Nos. 61605225, 11704238, and 61772295), the Educational Science and Technology Program of Shandong Province, China (Grant No. J18KZ012), and the Natural Science Foundation of Shanghai (Grant No. 16ZR1448400).

The quantum entanglement, discord, and coherence dynamics of two spins in the model of a spin coupled to a spin bath through an intermediate spin are studied. The effects of the important physical parameters including the coupling strength of two spins, the interaction strength between the intermediate spin and the spin bath, the number of bath spins and the temperature of the system on quantum coherence and correlation dynamics are discussed in different cases. The frozen quantum discord can be observed whereas coherence does not when the initial state is the Bell-diagonal state. At finite temperature, we find that coherence is more robust than quantum discord, which is better than entanglement, in terms of resisting the influence of environment. Therefore, quantum coherence is more tenacious than quantum correlation as an important resource.

Thermal and intrinsic decoherence effects on the dynamics of two three-level moving atomic system

We investigate the quantum Fisher information (QFI) and quantum entanglement (QE) dynamics of moving two three-level atoms interacting with a thermal field. The time evolution of the quantum system is studied numerically under the effect of intrinsic decoherence (ID) in a thermal environment. ID and thermal environment play a critical role during the time evolution of the quantum system. It is found that QE changes drastically when ID increases in the absence of atomic motion. However, a periodic behavior of QE is observed in the case of moving atoms. The thermal environment is seen to have a prominent effect on QFI in the presence of ID. Moreover, the decay of QE is further suppressed at larger time-scales which ensures the enhanced influence of ID on the system’s dynamics in a thermal environment. However, QFI and QE saturate to a lower level at larger time-scales under these environments. The behavior of QFI and QE is opposite to each other under these environments. Furthermore, it is seen that the thermal environment induces a faster decay of QE as compared to the decay induced by ID. Therefore, ID diminishes the degree of QE for higher-dimensional quantum systems. Moreover, the system’s dynamics changes remarkably by increasing the mean number of photons.

Dynamics of quantum information

The ability to harness the dynamics of quantum information and entanglement is necessary for the development of quantum technologies and the study of complex quantum systems. On the theoretical side the dynamics of quantum information is a topic that is helping us unify and confront common problems in otherwise disparate fields in physics, such as quantum statistical mechanics and cosmology. On the experimental side the impressive developments on the manipulation of neutral atoms and trapped ions are providing new capabilities to probe their quantum dynamics. Here, we overview and discuss progress in characterizing and understanding the dynamics of quantum entanglement and information scrambling in quantum many-body systems. The level of control attainable over both the internal and external degrees of freedom of individual particles in these systems provides great insight into the intrinsic connection between entanglement and thermodynamics, bounds on information transport and computational complexity of interacting systems. In turn this understanding should enable the realization of quantum technologies.

Sub-ballistic Growth of Rényi Entropies due to Diffusion

We investigate the dynamics of quantum entanglement after a global quench and uncover a qualitative difference between the behavior of the von Neumann entropy and higher Rényi entropies. We argue that the latter generically grow sub-ballistically, as ∝sqrt[t], in systems with diffusive transport. We provide strong evidence for this in both a U(1) symmetric random circuit model and in a paradigmatic nonintegrable spin chain, where energy is the sole conserved quantity. We interpret our results as a consequence of local quantum fluctuations in conserved densities, whose behavior is controlled by diffusion, and use the random circuit model to derive an effective description. We also discuss the late-time behavior of the second Rényi entropy and show that it exhibits hydrodynamic tails with three distinct power laws occurring for different classes of initial states.

Quantum Fisher Information and Entanglement of Moving Two Two-Level Atoms under the Influence of Environmental Effects

We have investigated numerically the dynamics of quantum Fisher information (QFI) and quantum entanglement (QE) of a two moving two-level atomic systems interacting with a coherent and thermal field in the presence of intrinsic decoherence (ID) and Kerr (non-linear medium) and Stark effects. The state of the entire system interacting with coherent and thermal fields is evaluated numerically under the influence of ID and Kerr (nonlinear) and Stark effects. QFI and von Neumann entropy (VNE) decrease in the presence of ID when the atomic motion is neglected. QFI and QE show an opposite response during its time evolution in the presence of a thermal environment. QFI is found to be more susceptible to ID as compared to QE in the presence of a thermal environment. The decay of QE is further damped at greater time-scales, which confirms the fact that ID heavily influences the system’s dynamics in a thermal environment. However, a periodic behavior of entanglement is observed due to atomic motion, which becomes modest under environmental effects. It is found that a non-linear Kerr medium has a prominent effect on the VNE but not on the QFI. Furthermore, it has been observed that QFI and QE decay soon under the influence of the Stark effect in the absence of atomic motion. The periodic response of QFI and VNE is observed for both the non-linear Kerr medium and the Stark effect in the presence of atomic motion. It is observed that the Stark, Kerr, ID, and thermal environment have significant effects during the time evolution of the quantum system.

Control of quantum entanglement and entropic uncertainty in open quantum system: Via adjusting Ohmic parameter

We investigate the dynamical behaviors of quantum entanglement and quantum-memory-assisted entropic uncertainty in the dephasing noise. The influence of Ohmic parameters and placement positions of the quantum register on the dynamics of quantum entanglement and entropic uncertainty are analyzed in detail. The numerical simulations show that the influence of Ohmic parameter at low temperature can be divided into two different regions in terms of the critical value s=2.5 . If s<2.5, the quantum entanglement decays monotonically with time, revealing the feature of Markovian dynamics. If s>2.5, the quantum entanglement decreases firstly and then raises and tends to a steady-state value. Thus, it is feasible to protect the quantum entanglement by choosing the super-Ohmic thermal reservoirs with s>2.5. This scheme is also beneficial to reduce entropic uncertainty. We find that, changing the positions of the quantum register do not affect the dynamics behavior and uncertainty of the system in the dephasing reservoir.

Entanglement Dynamics of Three and Four Level Atomic System under Stark Effect and Kerr-Like Medium

We investigated numerically the dynamics of quantum Fisher information (QFI) and entanglement for three- and four-level atomic systems interacting with a coherent field under the effect of Stark shift and Kerr medium. It was observed that the Stark shift and Kerr-like medium play a prominent role during the time evolution of the quantum systems. The non-linear Kerr medium has a stronger effect on the dynamics of QFI as compared to the quantum entanglement (QE). QFI is heavily suppressed by increasing the value of Kerr parameter. This behavior was found comparable in the cases of three- and four-level atomic systems coupled with a non-linear Kerr medium. However, QFI and quantum entanglement (QE) maintain their periodic nature under atomic motion. On the other hand, the local maximum value of QFI and von Neumann entropy (VNE) decrease gradually under the Stark effect. Moreover, no prominent difference in the behavior of QFI and QE was observed for three- and four-level atoms while increasing the value of Stark parameter. However, three- and four-level atomic systems were found equally prone to the non-linear Kerr medium and Stark effect. Furthermore, three- and four-level atomic systems were found fully prone to the Kerr-like medium and Stark effect.

Entanglement spreading and oscillation

We study dynamics of quantum entanglement in smooth global quenches with a finite rate, by computing the time evolution of entanglement entropy in 1 + 1 dimensional free scalar theory with time-dependent masses which start from a nonzero value at early time and either crosses or approaches zero. The time-dependence is chosen so that the quantum dynamics is exactly solvable. If the quenches asymptotically approach a critical point at late time, the early-time and late-time entropies are proportional to the time and subsystem size respectively. Their proportionality coefficients are determined by scales: in a fast limit, an initial correlation length; in a slow limit, an effective scale defined when adiabaticity breaks down. If the quenches cross a critical point, the time evolution of entropy is characterized by the scales: the initial correlation length in the fast limit and the effective correlation length in the slow limit. The entropy oscillates, and the entanglement oscillation comes from a coherence between right-moving and left-moving waves if we measure the entropy after time characterized by the quench rate. The periodicity of the late-time oscillation is consistent with the periodicity of the oscillation of zero modes which are zero-momentum value of two point functions of a fundamental field and its conjugate momentum.

The Quantum Entanglement Dynamics Induced by Non-Linear Interaction between a Moving Nano Molecule and a Two-Mode Field with Two-Photon Transitions Using Reduced Von Neumann Entropy and Jaynes-Cummings Model for Human Cancer Cells, Tissues and Tumors Diagnosis

The Quantum Entanglement Dynamics Induced by Non-Linear Interaction between a Moving Nano Molecule and a Two-Mode Field with Two-Photon Transitions Using Reduced Von Neumann Entropy and Jaynes-Cummings Model for Human Cancer Cells, Tissues and Tumors Diagnosis

Quantum Correlation in Squeezed Generalized Amplitude Damping Channels with Memory

A squeezed generalized amplitude damping (SGAD) channel is a quantum channel that models a general noise process incorporating the effects of bath squeezing, dissipation, and decoherence. In this paper, we analyze the dynamics of quantum entanglement and discord in the SGAD channel with memory. By obtaining a stochastic map defining this noisy quantum channel, we derive the concurrence and discord of Werner-like mixed states sent by successive uses of the channel. It is shown that these quantum correlations can be preserved or even generated depending on the initial channel input states, channel parameters, and the degree of channel memory. In particular, the squeezing effect does not contribute to the dynamics of quantum correlation for singlet-like states under correlated noise.

Stark and Kerr Effects on the Dynamics of Moving N-Level Atomic System

We have investigated numerically the dynamics of quantum Fisher information (QFI) and quantum entanglement (QE) for N-level atomic system interacting with a coherent field in the presence of Kerr (linear and non-linear medium) and Stark effects. It is observed that the Stark and Kerr effects play a prominent role during the time evolution of the quantum system. The evolving quantum Fisher information (QFI) is noted as time grows under the non-linear Kerr medium contrary to the QE for higher dimensional systems. The effect of non-linear Kerr medium is greater on the QE as we increase the value of Kerr parameter. However, QFI and QE maintain their periodic nature under atomic motion. On the other hand, linear Kerr medium has no prominent effects on the dynamics of N-level atomic system. Furthermore, it has been observed that QFI and QE decay soon under the influence of Stark effect. In short, the N-level atomic system is found prone to the change of the Kerr medium and Stark effect for higher dimensional systems.