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19 pages, 5698 KiB

Open AccessArticle

Decoherence Effects in a Three-Level System under Gaussian Process

by Sultan M. Zangi, Atta ur Rahman, Zhao-Xo Ji, Hazrat Ali and Huan-Guo Zhang

Symmetry 2022, 14(12), 2480; https://doi.org/10.3390/sym14122480 - 23 Nov 2022

Cited by 8 | Viewed by 2321

When subjected to a classical fluctuating field characterized by a Gaussian process, we examine the purity and coherence protection in a three-level quantum system. This symmetry of the three-level system is examined when the local random field is investigated further in the noiseless and noisy regimes. In particular, we consider fractional Gaussian, Gaussian, Ornstein–Uhlenbeck, and power law noisy regimes. We show that the destructive nature of the Ornstein–Uhlenbeck noise toward the symmetry of the qutrit to preserve encoded purity and coherence remains large. Our findings suggest that properly adjusting the noisy parameters to specifically provided values can facilitate optimal extended purity and coherence survival. Non-vanishing terms appear in the final density matrix of the single qutrit system, indicating that it is in a strong coherence regime. Because of all of the Gaussian noises, monotonic decay with no revivals has been observed in the single qutrit system. In terms of coherence and information preservation, we find that the current qutrit system outperforms systems with multiple qubits or qutrits using purity and von Neumann entropy. A comparison of noisy and noiseless situations shows that the fluctuating nature of the local random fields is ultimately lost when influenced using the classical Gaussian noises. Full article

(This article belongs to the Special Issue Advances in Quantum Information)

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17 pages, 464 KiB

Open AccessArticle

Relationship between Age and Value of Information for a Noisy Ornstein–Uhlenbeck Process

by Zijing Wang, Mihai-Alin Badiu and Justin P. Coon

Entropy 2021, 23(8), 940; https://doi.org/10.3390/e23080940 - 23 Jul 2021

Cited by 6 | Viewed by 2746

Abstract

The age of information (AoI) has been widely used to quantify the information freshness in real-time status update systems. As the AoI is independent of the inherent property of the source data and the context, we introduce a mutual information-based value of information (VoI) framework for hidden Markov models. In this paper, we investigate the VoI and its relationship to the AoI for a noisy Ornstein–Uhlenbeck (OU) process. We explore the effects of correlation and noise on their relationship, and find logarithmic, exponential and linear dependencies between the two in three different regimes. This gives the formal justification for the selection of non-linear AoI functions previously reported in other works. Moreover, we study the statistical properties of the VoI in the example of a queue model, deriving its distribution functions and moments. The lower and upper bounds of the average VoI are also analysed, which can be used for the design and optimisation of freshness-aware networks. Numerical results are presented and further show that, compared with the traditional linear age and some basic non-linear age functions, the proposed VoI framework is more general and suitable for various contexts. Full article

(This article belongs to the Special Issue Age of Information: Concept, Metric and Tool for Network Control)

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