Abstract This study explores quantum features, namely negativity, quantum-memory entropic uncertainty, entropic coherence, and linear entropy in a two-qubit mixture system comprising two Bell states under various classical environments. Furthermore, we assume including pure noise (colored pink, colored brown, Gaussian) and mixed noise (brown-Gaussian, pink-Gaussian) characterizing the classical environments. The influence of the purity parameter of the system along with the inclusive noise parameters is systematically analyzed. The entropic coherence and negativity functions remain sensitive to the noise showing larger revivals compared to the quantum-memory and coherence functions. The interplay between different types of noise leads to interesting dynamics, such as the suppression of Gaussian noise’s Markovian behavior by non-Markovian brown noise. Interestingly, the non-Markovian traits of pink noise are highly suppressed when combined with Gaussian noise. Besides, in mixed noise scenarios, non-regular fluctuations contrast with regular revivals in pure noise cases. The brown-Gaussian mixed noise case reveals the suppression of Gaussian noise’s Markovian behavior by non-Markovian brown noise, influencing overall dynamics. Notably, this scenario shows slight entanglement generation, unusual under classical environments, highlighting unique dynamics in mixed noise scenarios.
Abstract This study explores quantum features, namely negativity, quantum-memory entropic uncertainty, entropic coherence, and linear entropy in a two-qubit mixture system comprising two Bell states under various classical environments. Furthermore, we assume including pure noise (colored pink, colored brown, Gaussian) and mixed noise (brown-Gaussian, pink-Gaussian) characterizing the classical environments. The influence of the purity parameter of the system along with the inclusive noise parameters is systematically analyzed. The entropic coherence and negativity functions remain sensitive to the noise showing larger revivals compared to the quantum-memory and coherence functions. The interplay between different types of noise leads to interesting dynamics, such as the suppression of Gaussian noise’s Markovian behavior by non-Markovian brown noise. Interestingly, the non-Markovian traits of pink noise are highly suppressed when combined with Gaussian noise. Besides, in mixed noise scenarios, non-regular fluctuations contrast with regular revivals in pure noise cases. The brown-Gaussian mixed noise case reveals the suppression of Gaussian noise’s Markovian behavior by non-Markovian brown noise, influencing overall dynamics. Notably, this scenario shows slight entanglement generation, unusual under classical environments, highlighting unique dynamics in mixed noise scenarios.
Abstract We address entanglement, coherence, and information protection in a system of four non-interacting qubits coupled with different classical environments, namely: common, bipartite, tripartite, and independent environments described by Ornstein–Uhlenbeck (ORU) noise. We show that quantum information preserved by the four qubit state is more dependent on the coherence than the entanglement using time-dependent entanglement witness, purity, and Shannon entropy. We find these two quantum phenomena directly interrelated and highly vulnerable in environments with ORU noise, resulting in the pure exponential decay of a considerable amount. The current Markovian dynamical map, as well as suppression of the fluctuating character of the environments, are observed to be entirely attributable to the Gaussian nature of the noise. The increasing number of environments are witnessed to speed up the amount of decay. Unlike other noises, the current noise parameter’s flexible range is readily exploitable, ensuring long enough preserved memory properties. The four-qubit GHZ state, besides having a large information storage potential, stands partially entangled and coherent in common environments for an indefinite duration. In addition, we derive computational values for each system-environment interaction, which will help quantum practitioners to optimize the related classical environments.
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.
We analyzed the effect of colored noise on the negativity dynamics of a hybrid system consisting of a qubit–qutrit and not interacting, prepared from the start in an entangled one-parameter state and acting with noise in local and non-local environments. In this pink and brown noise we investigated two different situations: in the first situation, the noise is produced by a bistable oscillator with an unknown exchange rate; however, in the second situation, the noise is generated by a set of bistable oscillators. We found that entanglement decreases with time to zero, and undergoes the phenomenon of sudden death and rebirth. The pink noise is more prone to entanglement than the brown noise and the non-local environment is more prone to entanglement than the local one. When the number of fluctuators is increased, entanglement decays faster and finally, for certain parameters of the initial state, the subsystems are not affected by the noise.
Abstract We address the dynamics of the lower bound of geometric quantum discord and quantum-memory-assisted entropic uncertainty in a two-qutrit system when exposed to classical channels characterized by power-law (PL) and random telegraph (RT) noises. The system-channel coupling strategy is examined in two contexts: common qutrit-environment (CQE) and different qutrit-environment (DQE) configurations. We show that the geometric quantum discord functions remain anti-correlated with entropic uncertainty and decline as uncertainty appears in the system. The rate of entropic uncertainty appearance seems more prevalent than the decline rate of quantum discord function, suggesting that uncertainty causes the quantum correlations to fade in quantum systems. We find that non-local correlations estimated by the lower bound of geometric quantum discord are not destroyed even at the maximum entropic disorder and entropic uncertainty. In addition, the efficacy of entropic uncertainty and the lower bound is strongly influenced by the state’s purity factor, with the former being more robust at higher purity values and the latter at lower purity values. All the parameters impact entropic uncertainty, however, the mixedness of the state is noticed to greatly alter the generation of quantum memory. Besides, PL noise caused Markovian behavioral dynamics, and the RT noise allowed non-Markovian dynamics, while the latter remains more resourceful for the quantum correlations preservation and entropic uncertainty suppression. We also demonstrate how to model longer quantum correlations and provide optimal parameter settings for suppressing the dephasing and entropic uncertainty effects.
The dynamical map of entanglement and mixedness in four-qubit maximally entangled GHZ state paired with classical channels driven by fractional Gaussian noise is investigated. The qubit-channel coupling is assumed in four distinct ways: common, bipartite, tripartite, and independent local channel-qubit configurations comprising single, double, triple, or independent noisy sources. Using entanglement witness, negativity, purity and von Neumann entropy, except for the independent configuration, we show that indefinite entanglement and purity preservation may be simulated in multipartite GHZ-like states. Quantum correlations and purity decrease exponentially in four qubits, and exact fluctuating local field behaviour, as well as entanglement sudden death and birth revivals, are completely suppressed. Entanglement and purity preservation are affected by noise and the number of independent channels utilised. The Hurst parameter of fractional Gaussian noise was discovered in the four qubits to improve entanglement and avoid mixedness. Different entanglement and mixedness criteria yield different results, emphasizing the need to investigate various approaches in order to uncover multipartite correlations.
Abstract We address the time evolution of quantum correlations (QCs) such as entanglement, purity, and coherence for a model of two non-interacting qubits initially prepared as a maximally entangled bipartite state. We contrast the comparative potential of the classical fields to preserve these QCs in the noisy and noiseless realms. We also disclose the characteristic dynamical behavior of the QCs of the two-qubit state under the static noise effects originating from the common and different configuration models. We show that there is a direct connection between the fluctuations allowed by an environment and the preservation of QCs. Due to the static noise dephasing effects, the QCs are suppressed, resulting in the separability of the two-qubit entangled state after a finite duration. For bipartite QCs preservation, we show that the common configuration is more resourceful than the different configuration. Furthermore, this protection of the QCs under static noise for large intervals is entirely attributable to the existence of the entanglement sudden death and birth phenomenon. Most importantly, we found the bipartite QCs less fragile than the tripartite ones in comparison under the static noise. In addition, we find the concurrence measure to show more evident revivals of entanglement in comparison.