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Open AccessArticle

Quantifying Unknown Multiqubit Entanglement Using Machine Learning

by Yukun Wang, Shaoxuan Wang, Jincheng Xing, Yuxuan Du and Xingyao Wu

Entropy 2025, 27(2), 185; https://doi.org/10.3390/e27020185 - 12 Feb 2025

Viewed by 1242

Entanglement plays a pivotal role in numerous quantum applications, and as technology progresses, entanglement systems continue to expand. However, quantifying entanglement is a complex problem, particularly for multipartite quantum states. The currently available entanglement measures suffer from high computational complexity, and for unknown multipartite entangled states, complete information about the quantum state is often necessary, further complicating calculations. In this paper, we train neural networks to quantify unknown multipartite entanglement using input features based on squared entanglement (SE) and outcome statistics data produced by locally measuring target quantum states. By leveraging machine learning techniques to handle non-linear relations between outcome statistics and entanglement measurement SE, we achieve high-precision quantification of unknown multipartite entanglement states with a linear number of measurements, avoiding the need for global measurements and quantum state tomography. The proposed method exhibits robustness against noise and extends its applicability to pure and mixed states, effectively scaling to large-scale multipartite entanglement systems. The results of the experiment show that the predicted entanglement measures are very close to the actual values, which confirms the effectiveness of the proposed method. Full article

(This article belongs to the Special Issue Quantum Computing for Complex Dynamics, 2nd Edition)

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15 pages, 3739 KB

Open AccessArticle

Entanglement Swapping and Swapped Entanglement

by Sultan M. Zangi, Chitra Shukla, Atta ur Rahman and Bo Zheng

Entropy 2023, 25(3), 415; https://doi.org/10.3390/e25030415 - 25 Feb 2023

Cited by 23 | Viewed by 5642

Abstract

Entanglement swapping is gaining widespread attention due to its application in entanglement distribution among different parts of quantum appliances. We investigate the entanglement swapping for pure and noisy systems, and argue different entanglement quantifiers for quantum states. We explore the relationship between the entanglement of initial states and the average entanglement of final states in terms of concurrence and negativity. We find that if initial quantum states are maximally entangled and we make measurements in the Bell basis, then average concurrence and average negativity of final states give similar results. In this case, we simply obtain the average concurrence (average negativity) of the final states by taking the product of concurrences (negativities) of the initial states. However, the measurement in non-maximally entangled basis during entanglement swapping degrades the average swapped entanglement. Further, the product of the entanglement of the initial mixed states provides an upper bound to the average swapped entanglement of final states obtained after entanglement swapping. The negativity work well for weak entangled noisy states but concurrence gives better results for relatively strong entanglement regimes. We also discuss how successfully the output state can be used as a channel for the teleportation of an unknown qubit. Full article

(This article belongs to the Special Issue Quantum Entanglement and Quantum Computer)

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15 pages, 306 KB

Open AccessArticle

When Is a Genuine Multipartite Entanglement Measure Monogamous?

by Yu Guo

Entropy 2022, 24(3), 355; https://doi.org/10.3390/e24030355 - 28 Feb 2022

Cited by 8 | Viewed by 2916

Abstract

A crucial issue in quantum communication tasks is characterizing how quantum resources can be quantified and distributed over many parties. Consequently, entanglement has been explored extensively. However, there are few genuine multipartite entanglement measures and whether it is monogamous is so far unknown. In this work, we explore the complete monogamy of genuine multipartite entanglement measure (GMEM) for which, at first, we investigate a framework for unified/complete GMEM according to the unified/complete multipartite entanglement measure we proposed in 2020. We find a way of inducing unified/complete GMEM from any given unified/complete multipartite entanglement measure. It is shown that any unified GMEM is completely monogamous, and any complete GMEM that is induced by given complete multipartite entanglement measure is completely monogamous. In addition, the previous GMEMs are checked under this framework. It turns out that the genuinely multipartite concurrence is not as good of a candidate as GMEM. Full article

(This article belongs to the Special Issue Quantum Information and Computation)

15 pages, 2537 KB

Open AccessArticle

Spatio-Temporal Variability of Anthropogenic and Natural Wrack Accumulations along the Driftline: Marine Litter Overcomes Wrack in the Northern Sandy Beaches of Portugal

by Laura Guerrero-Meseguer, Puri Veiga and Marcos Rubal

J. Mar. Sci. Eng. 2020, 8(12), 966; https://doi.org/10.3390/jmse8120966 - 26 Nov 2020

Cited by 19 | Viewed by 3755

Abstract

Marine litter can end up deposited on sandy beaches and become entangled in the natural wrack, threatening its roles in ecosystems. However, it is currently unknown whether the storage of both artificial and natural accumulations on sandy beaches is correlated. Here, we quantified and compared, by first time, the litter and natural wrack on five sandy beaches in the north of Portugal. Results showed that the amount of marine litter and natural wrack were not correlated. Most of the sandy beaches had more litter than wrack and both artificial and natural accumulations disclosed high spatio-temporal variability. In summer, annual and opportunistic macroalgae dominated the wrack, while the litter was mainly formed by cigarette butts and leftover food. In winter, perennial taxa were more abundant in the wrack and plastics from mussel farming and cotton bud sticks dominated the litter. The macroalga Fucus spp., plastic pieces and materials from fishing were frequent in both periods. This study confirms that, currently, more litter than natural wrack reaches the Northern Portuguese sandy beaches, evidencing the need to take urgent measures against this contamination. Future management measures should consider this spatio-temporal variability to quantify both depositions. Full article

(This article belongs to the Section Marine Environmental Science)

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10 pages, 618 KB

Open AccessEditor’s ChoiceArticle

Measuring the Tangle of Three-Qubit States

by Adrián Pérez-Salinas, Diego García-Martín, Carlos Bravo-Prieto and José I. Latorre

Entropy 2020, 22(4), 436; https://doi.org/10.3390/e22040436 - 11 Apr 2020

Cited by 15 | Viewed by 6041

Abstract

We present a quantum circuit that transforms an unknown three-qubit state into its canonical form, up to relative phases, given many copies of the original state. The circuit is made of three single-qubit parametrized quantum gates, and the optimal values for the parameters are learned in a variational fashion. Once this transformation is achieved, direct measurement of outcome probabilities in the computational basis provides an estimate of the tangle, which quantifies genuine tripartite entanglement. We perform simulations on a set of random states under different noise conditions to asses the validity of the method. Full article

(This article belongs to the Section Quantum Information)

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