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The concept of entanglement and separability of quantum states is relevant for several fields in physics. Still, there is a lack of effective operational methods to characterise these features. We propose a method to certify quantum…

Quantum Physics · Physics 2024-03-06 Ties-A. Ohst , Xiao-Dong Yu , Otfried Gühne , H. Chau Nguyen

Quantum entanglement is a unique correlation phenomenon in quantum mechanics, and the measurement of quantum entanglement plays an important role in quantum computing and quantum communication. Many mainstream entanglement criteria and…

Quantum Physics · Physics 2024-11-12 Hao-Nan Qiang , Jing-Ling Chen

Entanglement, a critical resource for quantum information processing, needs to be witnessed in many practical scenarios. Theoretically, witnessing entanglement is by measuring a special Hermitian observable, called entanglement witness…

Quantum Physics · Physics 2016-04-20 Xiao Yuan , Quanxin Mei , Shan Zhou , Xiongfeng Ma

We present a closest separable state to cluster states. We start by considering linear cluster chains and extend our method to cluster states that can be used as a universal resource in quantum computation. We reproduce known results for…

Quantum Physics · Physics 2013-03-04 Michal Hajdusek , Vlatko Vedral

Fault tolerant quantum computing relies on the ability to detect and correct errors, which in quantum error correction codes is typically achieved by projectively measuring multi-qubit parity operators and by conditioning operations on the…

Detecting entanglement in many-body quantum systems is crucial but challenging, typically requiring multiple measurements. Here, we establish the class of states where measuring connected correlations in just $\textit{one}$ basis is…

Quantum Physics · Physics 2024-04-05 Roopayan Ghosh , Sougato Bose

Photonic cluster states are a crucial resource for optical quantum computing. Recently a quantum dot single photon source has been demonstrated to produce strings of photons in a linear cluster state, but high photon loss rates make it…

Quantum Physics · Physics 2019-01-31 Thomas Nutz , Antony Milne , Pete Shadbolt , Terry Rudolph

We explore procedures to detect entanglement of unknown mixed states, which can be experimentally viable. The heart of the method is a hierarchy of simple feasibility problems, which provides sufficient conditions to entanglement. Our…

Quantum Physics · Physics 2010-06-03 Thiago O. Maciel , Reinaldo O. Vianna

We address the interaction of two Gaussian states interferring at a beam splitter and analyze the correlations exhibited by the resulting bipartite system. We demonstrate that nonlocal correlations (entanglement) arise if and only if the…

Quantum Physics · Physics 2015-05-27 Stefano Olivares , Matteo G. A. Paris

We propose a scalable approach to building cluster states of matter qubits using coherent states of light. Recent work on the subject relies on the use of single photonic qubits in the measurement process. These schemes have a low initial…

Quantum Physics · Physics 2009-11-13 Sebastien G. R. Louis , Kae Nemoto , W. J. Munro , T. P. Spiller

Entangled states play a fundamental role in Quantum Mechanics and are at the core of many contemporary applications, such as quantum communication and quantum computing. Therefore, determining whether a state is entangled or not is an…

Quantum Physics · Physics 2023-05-11 J. Cortés-Vega , J. F. Barra , L. Pereira , A. Delgado

This thesis explores the use of entangled states in quantum computation and quantum information science. Entanglement, a quantum phenomenon with no classical counterpart, has been identified as an important and quantifiable resource in many…

Quantum Physics · Physics 2008-08-12 Hyeyoun Chung

Entanglement is recognized as a key resource for quantum computation and quantum cryptography. For quantum metrology, the use of entangled states has been discussed and demonstrated as a means of improving the signal-to-noise ratio. In…

Quantum Physics · Physics 2007-05-23 C. F. Roos , M. Chwalla , K. Kim , M. Riebe , R. Blatt

We present a method to conduct both quantum state reconstruction and entanglement purification simultaneously that is advantageous in several respects over previous work in this direction, showing that the number of Bell pairs necessary to…

Quantum Physics · Physics 2026-02-23 Takafumi Oka , Michal Hajdušek , Shota Nagayama , Rodney Van Meter

Entanglement purification is to distill high-quality entangled states from low-quality entangled states. It is a key step in quantum repeaters, determines the efficiency and communication rates of quantum communication protocols, and is…

Quantum Physics · Physics 2022-03-21 Cen-Xiao Huang , Xiao-Min Hu1 , Bi-Heng Liu , Lan Zhou , Yu-Bo Sheng , Chuan-Feng Li , Guang-Can Guo

Among various multipartite entangled states, Dicke states stand out because their entanglement is maximally persistent and robust under particle losses. Although much attention has been attracted for their potential applications in quantum…

Quantum Physics · Physics 2019-10-11 Ye-Chao Liu , Xiao-Dong Yu , Jiangwei Shang , Huangjun Zhu , Xiangdong Zhang

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 fidelity estimation between two quantum states is crucial for quantum computation and information science. However, an efficacious method for this, especially for mixed states and higher-dimensional density matrices, remains elusive.…

Quantum Physics · Physics 2026-05-11 Anumita Mukhopadhyay , Shibdas Roy , Arun Kumar Pati

Quantum entangled states have shown distinguished features beyond any classical state. Many methods like quantum state tomography have been presented to verify entanglement. In this work, we aim to identify unknown entanglements with…

Quantum Physics · Physics 2021-11-29 Ming-Xing Luo , Shao-Ming Fei , Jing-Ling Chen

Entanglement is a key property in the development of quantum technologies and in the study of quantum many-body simulations. However, entanglement measurement typically requires quantum full-state tomography (FST). Here we present a neural…

Quantum Physics · Physics 2022-09-20 Yulei Huang , Liangyu Che , Chao Wei , Feng Xu , Xinfang Nie , Jun Li , Dawei Lu , Tao Xin