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Two-qubit systems typically employ 36 projective measurements for high-fidelity tomographic estimation. The overcomplete nature of the 36 measurements suggests possible robustness of the estimation procedure to missing measurements. In this…

Quantum Physics · Physics 2020-12-08 Onur Danaci , Sanjaya Lohani , Brian T. Kirby , Ryan T. Glasser

Detection of entanglement is an indispensable step to practical quantum computation and communication. Compared with the conventional entanglement witness method based on fidelity, we propose a flexible, machine learning assisted…

Quantum Physics · Physics 2022-11-11 Jue Xu , Qi Zhao

Quantum neural networks (QNNs) have been a promising framework in pursuing near-term quantum advantage in various fields, where many applications can be viewed as learning a quantum state that encodes useful data. As a quantum analog of…

Quantum Physics · Physics 2023-09-27 Hao-kai Zhang , Chenghong Zhu , Mingrui Jing , Xin Wang

Understanding the relationship between various different forms of nonclassicality and their resource character is of great importance in quantum foundation and quantum information. Here, we discuss a quantitative link between quantum…

Quantum Physics · Physics 2026-01-01 Agung Budiyono

Quantum correlation between nodes in a network which consist of several independent sources of entanglement and in multipartite entanglement systems are important for general understanding of the nature of nonlocality, quantum information…

Quantum Physics · Physics 2022-01-25 E. Håkansson , A. Piveteau , S. Muhammad , M. Bourennane

Entanglement is a central resource in quantum information and quantum technologies, yet its characterization remains challenging due to both theoretical complexity and measurement requirements. Machine learning has emerged as a promising…

Quantum Physics · Physics 2026-02-05 A. García-Velo , R. Puebla , Y. Ban , E. Torrontegui , M. Paraschiv

Higher dimensional quantum systems are an important avenue for new explorations in quantum computing as well as quantum communications. One of the ubiquitous resources in quantum technologies is entanglement. However, so far, entanglement…

Quantum Physics · Physics 2019-09-05 Debadrita Ghosh , Thomas Jennewein , Urbasi Sinha

Entanglement not only plays a crucial role in quantum technologies, but is key to our understanding of quantum correlations in many-body systems. However, in an experiment, the only way of measuring entanglement in a generic mixed state is…

Quantum Physics · Physics 2018-10-16 Johnnie Gray , Leonardo Banchi , Abolfazl Bayat , Sougato Bose

Quantum networks comprised of entangled end nodes serve stronger than the classical correlation for unparalleled quantum internet applications. However, practical quantum networking is affected by noise, which at its worst, causes end nodes…

Quantum measurements are inherently noisy, hindering reliable entanglement detection and limiting the scalability of quantum technologies. While error mitigation and correction strategies exist, they often impose prohibitive resource…

Quantum Physics · Physics 2025-10-21 Mahmoud Mahdian , Ali Babapour-Azar , Zahra Mousavi , Rashed Khanjani-Shiraz

Several proposals have been recently introduced to implement Quantum Machine Learning (QML) algorithms for the analysis of classical data sets employing variational learning means. There has been, however, a limited amount of work on the…

Quantum Physics · Physics 2022-10-04 Francesco Scala , Stefano Mangini , Chiara Macchiavello , Daniele Bajoni , Dario Gerace

We revisit the application of neural networks techniques to quantum state tomography. We confirm that the positivity constraint can be successfully implemented with trained networks that convert outputs from standard feed-forward neural…

Quantum Physics · Physics 2022-07-20 D. Koutny , L. Motka , Z. Hradil , J. Rehacek , L. L. Sanchez-Soto

Density matrices are the most general descriptions of quantum states, covering both pure and mixed states. Positive semidefiniteness is a physical requirement of density matrices, imposing nonnegative probabilities of measuring physical…

Quantum Physics · Physics 2024-09-11 Colm Kelleher

Measurements are essential for the processing and protection of information in quantum computers. They can also induce long-range entanglement between unmeasured qubits. However, when post-measurement states depend on many non-deterministic…

When working with quantum states, analysis of the final quantum state generated through probabilistic measurements is essential. This analysis is typically conducted by constructing the density matrix from either partial or full tomography…

Quantum Physics · Physics 2025-01-14 Rohit Prasad , Pratyay Ghosh , Ronny Thomale , Tobias Huber-Loyola

In this study, we introduce an autonomous method for addressing the detection and classification of quantum entanglement, a core element of quantum mechanics that has yet to be fully understood. We employ a multi-layer perceptron to…

Quantum Physics · Physics 2024-10-21 Julio Ureña , Antonio Sojo , Juani Bermejo , Daniel Manzano

We report the experimental reconstruction of a nonclassicality quasiprobability for a single-photon added thermal state. This quantity has significant negativities, which is necessary and sufficient for the nonclassicality of the quantum…

Quantum Physics · Physics 2015-03-17 T. Kiesel , W. Vogel , M. Bellini , A. Zavatta

A major bottleneck in the quest for scalable many-body quantum technologies is the difficulty in benchmarking their preparations, which suffer from an exponential `curse of dimensionality' inherent to their quantum states. We present an…

Quantum Physics · Physics 2019-07-31 Juan Carrasquilla , Giacomo Torlai , Roger G. Melko , Leandro Aolita

Uncertainty quantification (UQ) is important for reliability assessment and enhancement of machine learning models. In deep learning, uncertainties arise not only from data, but also from the training procedure that often injects…

Machine Learning · Statistics 2023-11-13 Ziyi Huang , Henry Lam , Haofeng Zhang

We demonstrate in a superconducting qubit the conditional recovery ("uncollapsing") of a quantum state after a partial-collapse measurement. A weak measurement extracts information and results in a non-unitary transformation of the qubit…