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The use of advanced quantum neuron models for pattern recognition applications requires fault tolerance. Therefore, it is not yet possible to test such models on a large scale in currently available quantum processors. As an alternative, we…

Quantum Physics · Physics 2022-02-18 London A. Cavaletto , Luca Candelori , Alex Matos-Abiague

Quantum states that remain separable (i.e., not entangled) under any global unitary transformation are known as absolutely separable and form a convex set. Despite extensive efforts, the complete characterization of this set remains largely…

We present a class of linear correlation witnesses that detects bound entanglement within a three-party prepare-and-measure scenario with four-dimensional quantum messages. We relate the detection power of our witnesses for two-ququart…

Quantum Physics · Physics 2025-10-31 István Márton , Erika Bene , Tamás Vértesi

Bipartite states with vanishing quantum discord are necessarily separable and hence positive partial transpose (PPT). We show that 2 x N states satisfy additional property: the positivity of their partial transposition is recognized with…

Quantum Physics · Physics 2013-05-29 Bogna Bylicka , Dariusz Chruscinski

We give a separability criterion for three qubit states in terms of diagonal and anti-diagonal entries. This gives us a complete characterization of separability when all the entries are zero except for diagonal and anti-diagonals. The…

Quantum Physics · Physics 2017-09-13 Lin Chen , Kyung Hoon Han , Seung-Hyeok Kye

In this Letter, we show that the fulfillment of uncertainty relations is a sufficient criterion for a quantum-mechanically permissible state. We specifically construct two pseudo-spin observables for an arbitrary non-positive Hermitian…

Quantum Physics · Physics 2009-11-13 Hyunchul Nha , M. Suhail Zubairy

We analyze the separability properties of density operators supported on $\C^2\otimes \C^N$ whose partial transposes are positive operators. We show that if the rank of $\rho$ equals N then it is separable, and that bound entangled states…

Quantum Physics · Physics 2009-10-31 B. Kraus , J. I. Cirac , S. Karnas , M. Lewenstein

Quantum technologies require methods for preparing and manipulating entangled multiparticle states. However, the problem of determining whether a given quantum state is entangled or separable is known to be an NP-hard problem in general,…

Quantum Physics · Physics 2022-10-17 M. A. Gavreev , A. S. Mastiukova , E. O. Kiktenko , A. K. Fedorov

A group of symmetric operators are introduced to carry out the separability criterion for bipartite and multipartite quantum states. Every symmetric operator, represented by a symmetric matrix with only two nonzero elements, and their…

Quantum Physics · Physics 2012-12-04 Jie-Hui Huang , Li-Yun Hu , Lei Wang , Shi-Yao Zhu

The quantum convolutional neural network (QCNN) is a promising quantum machine learning (QML) model that is expected to achieve quantum advantages in classically intractable problems. However, the QCNN requires a large number of…

Quantum Physics · Physics 2024-05-07 Koki Chinzei , Quoc Hoan Tran , Kazunori Maruyama , Hirotaka Oshima , Shintaro Sato

The so-called permutation separability criteria are simple operational conditions that are necessary for separability of mixed states of multipartite systems: (1) permute the indices of the density matrix and (2) check if the trace norm of…

Quantum Physics · Physics 2007-05-23 Pawel Wocjan , Michal Horodecki

Entanglement can hide in two fundamentally different ways. First, multi-copy correlations can carry information that no single-copy measurement on an unknown state is able to access. Second, bound entangled states possess a positive partial…

Quantum Physics · Physics 2026-05-15 Patrycja Tulewicz , Karol Bartkiewicz , Franco Nori

Quantifying the minimum entanglement needed to prepare quantum states and implement quantum processes is a key challenge in quantum information theory. In this work, we develop computable and faithful lower bounds on the entanglement cost…

Quantum Physics · Physics 2025-05-08 Xin Wang , Mingrui Jing , Chengkai Zhu

Physical transformations are described by linear maps that are completely positive and trace preserving (CPTP). However, maps that are positive (P) but not completely positive (CP) are instrumental to derive separability/entanglement…

Quantum Physics · Physics 2023-01-10 Maciej Lewenstein , Guillem Müller-Rigat , Jordi Tura , Anna Sanpera

Entanglement detection in high dimensional systems is a NP-hard problem since it is lacking an efficient way. Given a bipartite quantum state of interest free entanglement can be detected efficiently by the PPT-criterion (Peres-Horodecki…

Quantum Physics · Physics 2021-10-07 Beatrix C. Hiesmayr

Reliable methods for the classification and quantification of quantum entanglement are fundamental to understanding its exploitation in quantum technologies. One such method, known as Separable Neural Network Quantum States (SNNS), employs…

Quantum Physics · Physics 2021-06-15 Cillian Harney , Mauro Paternostro , Stefano Pirandola

It is very crucial to know that whether the quantum state generated in the experiment is entangled or not. In the literature, this topic was studied extensively and researchers proposed different approaches for the detection of mixed…

Quantum Physics · Physics 2023-05-02 Anu Kumari , Satyabrata Adhikari

Quantum states are the key mathematical objects in quantum mechanics, and entanglement lies at the heart of the nascent fields of quantum information processing and computation. However, there has not been a general, necessary and…

Quantum Physics · Physics 2024-10-10 Bang-Hai Wang

Entanglement, or quantum inseparability, is a crucial resource in quantum information applications, and therefore the experimental generation of separated yet entangled systems is of paramount importance. Experimental demonstrations of…

Quantum Physics · Physics 2009-11-07 M. G. Raymer , A. C. Funk , B. C. Sanders , H. de Guise

We study the computational complexity of quantum discord (a measure of quantum correlation beyond entanglement), and prove that computing quantum discord is NP-complete. Therefore, quantum discord is computationally intractable: the running…

Quantum Physics · Physics 2014-03-31 Yichen Huang
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