Dynamics Of Quantum Correlations Research Articles

Controlling sudden transition between classical and quantum decoherence via squeezing phase of the baths

Correlations in the open quantum systems exhibit a rich phenomenology in various decoherent environments. We theoretically study the dynamics of quantum and classical correlations in a two-qubit system, where each qubit is locally subjected to the relevant squeezed vacuum bath through the non-demolition interaction. Specifically, we unveil the effects of the squeezing phase of the bath and squeezing strength on the intriguing phenomena of freezing discord and sudden transition between classical and quantum decoherence. Remarkably, we show that by proper tuning the squeezing phase one can significantly delay the sudden transition time . Interestingly, we found that the maximum delay in may obtain when the phase difference between the squeezing phase and the phase of the coupling strength is π/2. Consequently, an increase in the leads to the enhancement of time-interval during which quantum discord does not affect by environmental noise. On the other hand, we show that squeezing strength plays a negative role in enhancing sudden transition time and preserving quantum discord. Furthermore, we also show that squeezed bath allows the existence of the time-invariant discord for a broader range of Ohmicity parameter s and initial condition ε. Strikingly our study renders new insights to control and sustain quantum correlations against the detrimental effects of decoherence beyond the conventional protocols.

Hierarchy of quantum correlations under non-Markovian dynamics

We investigate the dynamics of quantum correlations (QC) under the effects of reservoir memory, as a resource for quantum information and computation tasks. Quantum correlations of two-qubit systems are used for implementing quantum teleportation successfully, and for investigating how teleportation fidelity, violation of Bell-CHSH inequality, quantum steering and entanglement are connected with each other under the influence of noisy environments. Both Markovian and non-Markovian channels are considered, and it is shown that the decay and revival of correlations follow the hierarchy of quantum correlations in the state space. Noise tolerance of quantum correlations are checked for different types of unital and non-unital quantum channels, with and without memory. The quantum speed limit time $(\tau_{QSL})$ is investigated from the perspective of memory of quantum noise, and the corresponding dynamics is used to analyze the evolution of quantum correlations. We establish the connection between information backflow, quantum speed limit time and dynamics of quantum correlations for non-Markovian quantum channels.

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.

Dynamics of local quantum uncertainty and local quantum fisher information for a two-qubit system driven by classical phase noisy laser

In this paper, the dynamics of quantum correlation quantified by local quantum uncertainty (LQU) and local quantum Fisher information (LQFI) for two uncoupled qubits driven by classical phase noisy laser have been investigated. The results show that, both LQU and LQFI exhibit similar behaviours, either display exponential decay or oscillatory decay with revivals depending on the ratios of classical phase noisy laser rate and system-environment coupling strength. Beside, our results also confirm the amount of quantum correlation measured by LQU is strictly bounded by LQFI in an open system. Finally, we propose a scheme to protect quantum correlation against classical phase noisy laser with the technique of weak measurement and reversal.

Controlling Entropic Uncertainty and Quantum Correlation of a Bath of Spins

We investigate the dynamical behaviors of quantum-memory-assisted entropic uncertainty relation (QMA-EUR) and quantum correlation (both quantum entanglement and quantum discord) for a two-qubit system coupled to a spin environment by a z–x-type interaction. Our purpose is to find out how the QMA-EUR and quantum correlations are affected by the pre-designed factors of the environment, including initial spin environmental states and the coupling constants. The numerical results show that the initial environmental state has significant effect on the dynamics of quantum correlations of the central spin system. We find that the environment should be prepared in a block entangled state with Bell state. This option is beneficial to reducing entropic uncertainty and inhibits the damping of quantum correlation. We also find that the high frequency particles in a spin bath can significantly enhance the robustness of quantum correlation of the system.

Non-classicality of two superconducting-qubits interacting independently with a resonator cavity: trace-norm correlation and Bures-distance entanglement

We study the behaviour of the correlation robustness of two spatially isolated charge-qubits started initially with a maximally correlated nonsymmetric Bell-state. Each charged qubit is coupled individually to a superconducting resonator coherent field. The dynamics of the qubit-resonator quantum correlations, based on trace-norm measurement-induced non-locality (MIN) and Bures distance entanglement, are investigated under the effects of the qubit-resonator interactions, intrinsic decoherence, initial coherent intensity cavity as well as of the qubit-resonator detuning. It is found that the trace-norm MIN correlation can be enhanced by the initial coherent field intensity and the detuning. The MIN is more robust, against the qubit-resonator interactions and the decoherence, than the Bures distance entanglement. Furthermore, the correlation robustness analysed for the different cases of the coherent states depends not only on the intrinsic decoherence but also on the coherent states and the qubit-resonator detuning.

Dynamics of quantum correlation for three qubits in hierarchical environment

Much attention has been paid to the dynamics of quantum correlation in an open quantum system coupled to a single-layered environment for a long time. However, the system can be influenced by the multilayer environment or hierarchical environment in realistic scenarios, which is attracting increasing interest at present. In this context, we explore in this paper the dynamics of quantum correlation for a quantum system consisting of three independent qubits, each being immersed in a single mode lossy cavity which is further connected to another cavity. The influences of cavity-cavity coupling strength <i>Ω</i> and the decay rate of cavity <i>Γ</i><sub>1</sub> on the measures of quantum correlation, including negativity, Bell non-locality as well as entanglement witness, are investigated in detail in a strong coupling regime and a weak coupling regime. It is shown that the phenomena of sudden death and sudden birth can happen to both Bell non-locality and entanglement witness. When the decay rate <i>Γ</i><sub>1</sub> = 0 is given, with the increase of <i>Ω</i> these measures eventually reach their stationary values over time after a short period of damping oscillations, in which these stationary values will become larger for the larger <i>Ω</i>. At the same time, the values or the survival times of quantum correlation considered by us in the weak coupling regime are better than in the strong coupling case. In addition, the non-zero <i>Γ</i><sub>1</sub> has a great negative effect on quantum correlation. Hence, in order to suppress the loss of quantum correlation better, the effective manipulation of quantum weak measurement and measurement reversal operator is considered further. Some interesting results are obtained.

The dynamics of quantum correlations and quantum coherence ina classical colored noise

The dynamics of one-way information deficit, geometric quantum discord and quantum coherence in mixed bipartite qubit state in the presence of classical colored noise with 1/fα spectrum are investigated. The source of the noise spectrum is a single fluctuator with undetermined switching rate. The analysis is made under the frame work of collective coupling between the components of the system and environment. Qualitatively the responses of all the three quantities are similar to the noise, however, quantum coherence stands robust than the other two quantities. Depending on choice of the different regimes of the characteristic parameters of the noise, the decay in all the three quantities can be monotonic, damped oscillating or exhibiting sudden death with revivals.

Dynamics of Rydberg excitations and quantum correlations in an atomic array coupled to a photonic crystal waveguide

We study the dynamics of up to two Rydberg excitations and the correlation growth in a chain of atoms coupled to a photonic crystal waveguide. In this setup, an excitation can hop from one atom to another via exponentially decaying exchange interactions mediated by the waveguide. An initially localized excitation undergoes a continuous-time quantum walk for short-range hopping, and for long-range, it experiences quasi-localization. Besides that, the inverse participation ratio reveals a super-ballistic diffusion of the excitation in short times, whereas, at a long time, it becomes ballistic. For two initially localized excitations, intriguing, and complex dynamical scenarios emerge for different initial separations due to the competition between the Rydberg-Rydberg and exchange interactions. In particular, the two-point correlation reveals a light-cone behavior even for sufficiently long-range exchange interactions. Additionally, we characterize the growth of bipartite entanglement entropy, which exhibits a global bound if only one excitation is present in the dynamics. Finally, we analyze the effect of imperfections due to spontaneous emission from the Rydberg state into photons outside the waveguide and show that all physical phenomena we predict are well within experimental reach.

Quantum correlations dynamics in two coupled semiconductor InAs quantum dots

We investigate the dynamics of both quantum discord and concurrence within two excitonic qubits embedded in two coupled semiconductor quantum dots independently interacting with dephasing reservoirs. Their behavior in both Markovian and non-Markovian environments is explored against the dimensionless time and the temperature. Moreover, the effects of the external electric field on these correlations as well as the effects related to the Förster interaction are extensively analyzed. We show that the non-Markovian behavior of quantum correlations is always preserved under the variation of the electric field and the Förster interaction, regardless of the strong influence of these two parameters on the amount of quantum correlations. Furthermore, we show that nonzero discord can still be observed for large values of temperature and dimensionless time, unlike concurrence which vanishes in this regime.

Dynamics of quantum correlations for different types of noisy channels

The effect of noise channels (amplitude damping, phase damping, depolarizing and phase flip) on the behaviors of quantum correlations such as quantum discord (QD), super quantum discord (SQD) within an atom-field interaction with environments are investigated. Generation and preservation of the quantum entanglement between the qubit and field have played an important role for both fundamental quantum theories and experiments. This topic motivates us to explore the role of noise channels on quantum correlations in the Jaynes–Cummings model. Our analytical results show that the entanglement and quantum correlation dynamics is strongly related to the decoherenc strength and type of noisy channel. One purpose of this work is to answer the following question: is it possible the effects of noise channels on entangled states lead to birth of entanglement and quantum correlations or do they just have a destructive effects? We show that, the noise of all above channels do not lead to a sudden vanishing of quantum correlations. But the noise of phase flip channel reproduces initial quantum correlations. Furthermore, we find that entanglement and QD are more fragile to environmental noises than the SQD. For this reason, it seems that our results can be beneficial to deeply understanding the weak measurement and quantum correlation in quantum information resource.

Quantum Correlation Dynamics in Controlled Two-Coupled-Qubit Systems

We study and compare the time evolutions of concurrence and quantum discord in a driven system of two interacting qubits prepared in a generic Werner state. The corresponding quantum dynamics is exactly treated and manifests the appearance and disappearance of entanglement. Our analytical treatment transparently unveils the physical reasons for the occurrence of such a phenomenon, relating it to the dynamical invariance of the X structure of the initial state. The quantum correlations which asymptotically emerge in the system are investigated in detail in terms of the time evolution of the fidelity of the initial Werner state.

Magnetization revivals and dynamics of quantum correlations in a Kitaev spin chain

We investigate the dynamics of a spin chain with Kitaev-type interaction in a transverse magnetic field, for both a constant field and a periodically kicked field. We investigate analytically the revivals in the dynamical behavior of the magnetization, and measures of local quantum correlations, the concurrence measure of the entanglement, and the quantum discord. The magnetization revivals are seen even for larger chain lengths, with reduced revival peaks, both near and away from the critical point at zero magnetic field. The quantum entanglement and correlation measures, contrary to the expected behavior, exhibit reduced quantum correlations in the critical region, compared to the region away from the critical point. The concurrence is larger than the quantum discord away from the critical region. The pair entanglement is near zero for all times in the critical region, though the quantum discord is nonzero, capturing the underlying diagonal correlations. The kicked magnetic field dynamics shows similar evolution for the magnetization and quantum correlations. For special values of the kicking period, the concurrence shows alternates between zero and nonzero values for successive kicks in the noncritical region.

The Dynamics of Quantum Correlations of Two Qubits in a Common Environment

The Dynamics of Quantum Correlations of Two Qubits in a Common Environment

Dynamics of quantum correlations in quantum teleportation

A scheme of quantum teleportation using Jaynes–Cummings model is proposed. It consists of using a partial entangled state generated from the interaction between a two-level atom and single mode of radiation field as a quantum channel. By controlling the number of photons inside cavity and detuning parameter, the dynamical evolution of quantum correlation and entanglement degree in terms of quantum discord and concurrence, respectively, in the nonresonance case are investigated. Moreover, a comparative study between the teleported entanglement, teleported quantum correlation and average fidelity shows a good similarity between their dynamical evolution. Consequently, we conclude that quantum discord may be considered as a good information source in quantum teleportation process.

Phonon-mediated quantum discord in dark solitons

We investigate the quantum correlation dynamics in dark-soliton qubits with a special attention to quantum discord. Recently, dark-soliton qubit exhibiting appreciably long lifetime is proved to be an excellent candidate for information processing. Depending on the precise distance between the dark-soliton qubits, the decay rate of Dicke symmetric and antisymmetric state is suppressed or enhanced. With the Renyi-2 entropy, we derive a simple analytical expression for the quantum discord and explore the generation and decay of correlation for different initial states. We believe that the present work could pave the stage for a new generation of quantum discord based purely on matter-wave phononics.

Dynamics of Quantum Correlations in a Qubit-Oscillator System Interacting via a Dissipative Bath

The entanglement dynamics in a bipartite system consisting of a qubit and a harmonic oscillator interacting only through their coupling with the same bath is studied. The considered model assumes that the qubit is coupled to the bath via the Jaynes-Cummings interaction, whilst the position of the oscillator is coupled to the position of the bath via a dipole interaction. We give a microscopic derivation of the Gorini–Kossakowski–Sudarshan–Lindblad equation for the considered model. Based on the Kossakowski matrix, we show that non-classical correlations including entanglement can be generated by the considered dynamics. We then analytically identify specific initial states for which entanglement is generated. This result is also supported by our numerical simulations.

New properties of a pure bipartite system in presence of dissipative environments

We investigate some new properties of the model of a pure bipartite system in dissipative environments. The mathematical model of bipartite system with the interaction cavity field in the presence of dissipative environment is designed. The systems is assumed to be initially in the Warner state. The system is analytically solved using master equation method. We quantified the dynamics of quantum correlation between the system, under the influence of the mean photon numbers, type of the initial state and spontaneous emission rate of atom using several measures are, measurement-induced disturbance (MID) and Geometric measure of quantum discord (GQD), negativity (N) and concurrence (C). The effect of the system parameters on dynamics of entanglement is investigated, it is found that the spontaneous emission rate of atom number have much effect on all measures. Moreover the Geometric measure of quantum discord (GQD) have different behavior rather than the others and more influenced by the mean photon number and type of the initial state.

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.

Dynamics and protection of quantum correlations in a qubit–qutrit system subjected locally to a classical random field and colored noise

This paper investigates the evolution and protection of quantum correlations (entanglement and quantum discord (QD) in particular), in a hybrid system formed by a qubit subjected to an external random field and a qutrit subjected to a colored noise generated either by a single or collection of many random bistable fluctuators (RBFs). Two different input states namely the one- and two-parameter class of states of qubit–qutrit are investigated. Entanglement and QD are quantified by means of negativity and geometric QD and their protection investigated by recourse to the weak measurement (WM) and weak measurement reversal (WMR) technique. It is shown that the immunity of entanglement and QD against decoherence can be efficiently increased by properly adjusting the parameters of the input states, no matter the spectrum of the colored noise and the number of RBFs considered. Moreover, it is shown that the WM and WMR technique fails in protecting entanglement in the studied system, but can effectively protect QD from the detrimental impacts of the decoherence. In fact, it is shown that performing a WM followed by a WMR on the qubit of the system allows to shield the QD of the system from decoherence even when the decoherence process is strengthen by considering a large number of RBFs affecting the qutrit.