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We introduce an entanglement criterion to exclude full separability of quantum states. We present numerical evidence that the criterion is necessary and sufficient for the class of GHZ diagonal three-qubit states and estimate the volume of…

Quantum Physics · Physics 2011-01-04 Otfried Gühne

Noise remains the major obstacle to scalable quantum computation. Quantum benchmarking provides key information on noise properties and is an important step for developing more advanced quantum processors. However, current benchmarking…

Quantum Physics · Physics 2023-09-22 Yanwu Gu , Wei-Feng Zhuang , Xudan Chai , Dong E. Liu

The entanglement criterion for continuous variable systems and the conditions under which the uncertainty relations are fulfilled are generalized to the case of a noncommutative (NC) phase-space. The quantum nature and the separability of…

In quantum information and computation, the generation of entanglement through unitary gates remains a significant and active area of research. However, there are states termed as absolutely separable, from which entanglement cannot be…

Quantum Physics · Physics 2026-02-13 Bivas Mallick , Saheli Mukherjee , Nirman Ganguly , A. S. Majumdar

We define a negative entanglement measure for separable states which shows that how much entanglement one should compensate the unentangled state at least for changing it into an entangled state. For two-qubit systems and some special…

Quantum Physics · Physics 2015-05-18 Cheng-Jie Zhang , Yong-Jian Han , Yong-Sheng Zhang , Yu-Chun Wu , Xiang-Fa Zhou , Guang-Can Guo

Characterizing entanglement is central for quantum information science. Special observables which indicate entanglement, so-called entanglement witnesses, are a widely used tool for this task. The construction of these witnesses typically…

Quantum Physics · Physics 2024-09-30 Chengjie Zhang , Sophia Denker , Ali Asadian , Otfried Gühne

Entanglement is a key issue in the quantum physics which gives rise to resources for achieving tasks that are not possible within the realm of classical physics. Quantum entanglement varies with the evolution of the quantum systems. It is…

Quantum Physics · Physics 2019-06-06 Long-Mei , Yang Tao Li , Shao-Ming Fei , Zhi-Xi Wang

Employing a recently proposed separability criterion we develop analytical lower bounds for the concurrence and for the entanglement of formation of bipartite quantum systems. The separability criterion is based on a nondecomposable…

Quantum Physics · Physics 2007-05-23 Heinz-Peter Breuer

Entanglement witnesses (EWs) are a collection of observables that can characterize separable states and, experimentally, estimating EWs can verify entangled states. In this work, we show that a fixed measurement setting on a multipartite…

Quantum Physics · Physics 2026-05-29 Jaemin Kim , Anindita Bera , Dariusz Chruściński , Joonwoo Bae

The information obtained from the operation of a quantum gate on only two complementary sets of input states is sufficient to estimate the quantum process fidelity of the gate. In the case of entangling gates, these conditions can be used…

Quantum Physics · Physics 2017-08-23 Holger F. Hofmann , Ryo Okamoto , Shigeki Takeuchi

Entanglement is a fundamental resource for many applications in quantum information processing. Here, we investigate how quantum transport in simple quantum graphs, modeled as controlled two-level quantum systems, can be utilized to…

Quantum Physics · Physics 2025-10-24 Alison A. Silva , D. Bazeia , Fabiano M. Andrade

This paper has been removed and is superceded by a pair of papers on stochastic maps, or channels, which break entanglement (EBT). quant-ph/0302031 General Entanglement Breaking Channels by Michael Horodecki, Peter W. Shor and Mary Beth…

Quantum Physics · Physics 2007-05-23 Mary Beth Ruskai

A typical bipartite quantum protocol, such as EPR-steering, relies on two quantum features, entanglement of states and incompatibility of measurements. Noise can delete both of these quantum features. In this work we study the behavior of…

Quantum Physics · Physics 2015-10-14 Teiko Heinosaari , Jukka Kiukas , Daniel Reitzner , Jussi Schultz

We present a description of finite dimensional quantum entanglement, based on a study of the space of all convex decompositions of a given density matrix. On this space we construct a system of real polynomial equations describing separable…

Quantum Physics · Physics 2008-08-27 J. K. Korbicz , F. Hulpke , A. Osterloh , M. Lewenstein

We present a way of identifying all kinds of entanglement for three-qubit pure states in terms of the expectation values of Pauli operators. The necessary and sufficient conditions to classify the fully separable, biseparable, and genuine…

Quantum Physics · Physics 2015-06-12 Ming-Jing Zhao , Ting-Gui Zhang , Xianqing Li-Jost , Shao-Ming Fei

Entanglement plays an important role in quantum communication, algorithms, and error correction. Schmidt coefficients are correlated to the eigenvalues of the reduced density matrix. These eigenvalues are used in Von Neumann entropy to…

Quantum Physics · Physics 2014-09-25 Anmer Daskin , Ananth Grama , Sabre Kais

A quantum state's entanglement across a bipartite cut can be quantified with entanglement entropy or, more generally, Schmidt norms. Using only Schmidt decompositions, we present a simple iterative algorithm to maximize Schmidt norms.…

Quantum Physics · Physics 2018-06-14 Robin Reuvers

Quantum correlation provides a promising measure beyond entanglement. Here, we propose a necessary and sufficient condition for nonzero quantum correlation in continuous variable systems, which is simple and easy to perform in terms of a…

Quantum Physics · Physics 2015-11-12 Chengjie Zhang , Sixia Yu , Qing Chen , Haidong Yuan , C. H. Lai , C. H. Oh

Multipartite entanglement is the key resource allowing quantum devices to outperform their classical counterparts, and entanglement certification is fundamental to assess any quantum advantage. The only scalable certification scheme relies…

Quantum Physics · Physics 2021-07-28 Irénée Frérot , Tommaso Roscilde

A key lesson of the decoherence program is that information flowing out from an open system is stored in the quantum state of the surroundings. Simultaneously, quantum measurement theory shows that the evolution of any open system when its…

Quantum Physics · Physics 2012-01-27 Juan Diego Urbina , Walter T. Strunz , Carlos Viviescas