Abstract When two qubits are prepared in a mixture of two Bell states and exposed to local transmission channels, the dynamics of steerability, Bell nonlocality, and average steered coherence are investigated. Disorders are assumed to influence the channels, resulting in either Markovian Ornstein–Uhlenbeck noise or non‐Markovian static noise in two models: a single noisy channel or two local noisy channels. Their findings show that the type and number of classical channels, noise, and initial state must be in an optimal setting in order to preserve quantum correlations.
Abstract When two qubits are prepared in a mixture of two Bell states and exposed to local transmission channels, the dynamics of steerability, Bell nonlocality, and average steered coherence are investigated. Disorders are assumed to influence the channels, resulting in either Markovian Ornstein–Uhlenbeck noise or non‐Markovian static noise in two models: a single noisy channel or two local noisy channels. Their findings show that the type and number of classical channels, noise, and initial state must be in an optimal setting in order to preserve quantum correlations.
Abstract The dephasing effects of two independent local mixed static‐Ornstein Uhlenbeck (STC‐OUK) noisy channels on the dynamics of two‐qubit non‐classical correlations, non‐locality, and entanglement are addressed. Here, i) local quantum Fisher information; ii) local quantum uncertainty; iii) uncertainty‐induced non‐locality; iv) Bell non‐locality; and v) negativity to quantify two‐qubit non‐classical correlations, non‐locality and entanglement, respectively, and their loss under the influence of mixed noise are used. The findings show that measure (i) compared to measure (ii) remains more effective in demonstrating non‐classical correlations. For the two‐qubit state with maximum purity, measure (iii) remains less fragile to the mixed STC‐OUK noise than measure (iv) but gets more vulnerable as the initial purity of the two‐qubit state falls. It is intriguing that measures (i), (ii), and (v) completely freeze after a particular interval, yet measures (iii) and (iv) remains partially preserved indefinitely. When compared to other two‐qubit correlation quantifiers, measure (v) exhibits non‐Markovian behavior and the phenomenon of sudden death and birth. Markovian and non‐Markovian dynamical maps, and extended two‐qubit correlations, can be induced by optimizing the current configuration. Finally, under the influence of mixed dephasing effects, robust and strengthened quantum correlations beyond entanglement in the two‐qubit Werner state is shown.
We address the dynamics of quantum coherence, quantum correlations, quantum steering and Bell nonlocality in a model of two interacting qubits, initially prepared in a thermal state. The two qubit are coupled via a dipolar interaction and exposed to Dzyaloshinskii–Moriya (DM) interaction and classical fluctuating fields influenced by Ornstein–Uhlenbeck (OU)-Static (ST) mixed noise in common environments. We analyse the dynamics effects on quantum resources, as Bell nonlocality, quantum steering, quantum entanglement, quantum discord and quantum coherence. We find that the dynamics of quantum correlations are not only strongly affected by the type of system-environment coupling but also by the kind of the considered noise. The entanglement diminution is over time, accompanied by damped oscillations, indicative of coherent dynamics. The DM interaction induces a decrease in quantum coherence and correlations with increasing values, leading to complete maximizing at critical thresholds. The effects of thermal effects destroy the quantum correlation. The variations in state noise disorder parameters reveal enhanced preservation and reduced oscillations as the noise disorder parameter decreases, emphasizing its crucial role in shaping quantum correlations.
Abstract We investigate how the correlations between consecutive actions of the two-qubit noisy channels affect quantum teleportation, entanglement, and Bell nonlocality. For the initial Bell and Werner states used for teleportation, we established connections among these three quantities, and obtained the minimum correlation strengths for achieving the nonclassical teleportation fidelity, nonvanishing entanglement, and Bell-nonlocal states. It was found that these three quantities can be noticeably enhanced due to the existence of the channel correlations. By considering a colored dephasing channel, we further investigated the combined effects of the channel correlation and the (non-)Markovianity of the channel on the teleportation fidelity, entanglement, and Bell nonlocality. The result shows that while they decrease monotonically with time in the Markovian regime, their strengths can be further enhanced due to the non-Markovian memory effect in a wide time region.
Abstract We investigate the dynamical maps of coherence, entanglement, and purity in two distinct three-qubit class states: the Werner (W-like) and Greeneberger–Horne–Zeillinger (GHZ-like) states. Utilizing a classical channel affected by Ornstein Uhlenbeck (OU) and Random Telegraph (RT) noise, we explore two scenarios: coupling two qubits with RT noise and one with OU noise, and vice versa . The preservation of coherence, entanglement, and purity is analyzed using the ℓ 1 norm of coherence, entanglement witness operation, and purity measures. Our results reveal that the considered dephasing channels lead to a decrease in initially encoded quantum correlations, even in the presence of Gaussian OU noise, which typically induces monotonic decay. The non-monotonic behavior and decay are primarily governed by the parameters of OU and RT noises, with the configuration where OU noise affects two qubits and RT noise affects the third being optimal for quantum correlation preservation. Comparing the two states, the GHZ-like state exhibits superior preservation under RT noise influencing two local fields and qubits, while the W-like state performs better when OU noise affects two qubits. Overall, the GHZ-like state shows enhanced revival characteristics compared to the W-like state.
We investigate the dynamics of entropic uncertainty relations, tightness, and concurrence in two non-interacting qubits produced in the Werner state and subjected to classical channels. In two contexts, common and independent qubit-noise configurations, a Gaussian Ornstein Uhlenbeck process is used to control the noisy effects of the local external fields. Using parameter optimization, we establish long-term stability in two qubits while reducing the environment's disorder entropic impact and maintaining entanglement. Using entropic uncertainty relations, tightness and concurrence, we show that in the presence of Ornstein Uhlenbeck noise, two-qubit coherence and entanglement in local fields are both weak and readily lost. Despite this, longer entanglement and lower entropy can be predicted within a limited range of the noise parameter and the purity estimator of the two-qubit state. Furthermore, the measured rate of entropy rise outpaces the rate of disentanglement generation. In addition, we also utilized the tightness measure to estimate the uncertainty in the dynamics of bipartite entropic relations.
Quantum nonlocality and nonclassicality are two remarkable characteristics of quantum theory, and offer quantum advantages in some quantum information processing. Motivated by recent work on the interplay between nonclassicality quantified by average correlation [Tschaffon et al., Phys. Rev. Res. 5,023063 (2023)] and Bell nonlocality, in this paper we aim to establish the relationship between the average correlation and the violation of the three-setting linear steering inequality for two-qubit systems. Exact lower and upper bounds of average correlation versus steering are obtained, and the respective states which suffice those bounds are also characterized. For clarity of our presentation, we illustrate these results with examples from well-known classes of two-qubit states. Moreover, the dynamical behavior of these two quantifiers is carefully analyzed under the influence of local unital and nonunital noisy channels. The results suggest that average correlation is closely related to the violation of three-setting linear steering, like its relationship with Bell violation. Particularly, for a given class of states, the hierarchy of nonclassicality-steering-Bell nonlocality is demonstrated.