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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

An entanglement witness approach to quantum coherent state key distribution and a system for its practical implementation are described. In this approach, eavesdropping can be detected by a change in sign of either of two witness functions,…

Quantum Physics · Physics 2015-06-16 David S. Simon , Gregg Jaeger , Alexander V. Sergienko

Quantum entanglement and decoherence are the two counterforces of many quantum technologies and protocols. For example, while quantum teleportation is fueled by a pair of maximally entangled resource qubits, it is vulnerable to decoherence.…

Entanglement witnesses form an effective method to locally detect entanglement in the laboratory without having the prior knowledge of the full density matrix. However, separable states can be erroneously indicated as entangled in such…

Quantum Physics · Physics 2021-08-04 Kornikar Sen , Chirag Srivastava , Shiladitya Mal , Aditi Sen De , Ujjwal Sen

Entanglement is one of the most prominent features of quantum mechanics and serves as an essential resource in quantum information science. Therefore, the certification of entanglement is crucial for quantum information processing tasks.…

Quantum Physics · Physics 2025-04-10 Jing-Tao Qiu , Wei-Jie Jiang , Xiao-Dong Yu

Entanglement is a key resource to demonstrate quantum advantage over classical strategies. Entanglement in quantum states is one of the most well-explored areas in quantum physics. However, a rigorous approach to understanding and detecting…

Quantum Physics · Physics 2025-02-12 Shubhayan Sarkar

Design of detection strategies for multipartite entanglement stands as a central importance on our understanding of fundamental quantum mechanics and has had substantial impact on quantum information applications. However, accurate and…

Quantum Physics · Physics 2023-05-24 Xin-Yu Xu , Qing Zhou , Shuai Zhao , Shu-Ming Hu , Li Li , Nai-Le Liu , Kai Chen

Nonclassical states are essential for optics-based quantum information processing, but their fragility limits their utility for practical scenarios in which loss and noise inevitably degrade, if not destroy, nonclassicality. Exploiting…

Quantum Physics · Physics 2015-03-25 Zheshen Zhang , Sara Mouradian , Franco N. C. Wong , Jeffrey H. Shapiro

We present entanglement witness operators for detecting genuine multipartite entanglement. These witnesses are robust against noise and require only two local measurement settings when used in an experiment, independent from the number of…

Quantum Physics · Physics 2007-05-23 Geza Toth , Otfried Guehne

The controlled generation of entangled states and their subsequent detection are integral aspects of quantum information science. In this work, we analyse the application of nonlinear witnesses to the verification of entanglement, and we…

Quantum Physics · Physics 2012-10-04 Megan Agnew , Jeff Z. Salvail , Jonathan Leach , Robert W. Boyd

It is well known that entanglement can benefit quantum information processing tasks. Quantum illumination, when first proposed, is surprising as entanglement's benefit survives entanglement-breaking noise. Since then, many efforts have been…

Quantum Physics · Physics 2021-06-16 Quntao Zhuang

The experimental verification of multipartite entangled states is essential for advancing quantum information processing. Entanglement witnesses (EWs) provide a widely used and experimentally accessible approach for detecting genuinely…

Quantum Physics · Physics 2025-09-03 Tomis Prajapati , Harsh Mehta , Shreya Banerjee , Prasanta K. Panigrahi , V. Narayanan

Entanglement detection is one of the most conventional tasks in quantum information processing. While most experimental demonstrations of high-dimensional entanglement rely on fidelity-based witnesses, these are powerless to detect…

Recent advances in quantum technologies are rapidly stimulating the building of quantum networks. With the parallel development of multiple physical platforms and different types of encodings, a challenge for present and future networks is…

Quantum Physics · Physics 2021-04-14 G. Guccione , T. Darras , H. Le Jeannic , V. B. Verma , S. W. Nam , A. Cavaillès , J. Laurat

Quantum computing holds unparalleled potentials to enhance machine learning. However, a demonstration of quantum learning advantage has not been achieved so far. We make a step forward by rigorously establishing a noise-robust,…

Quantum Physics · Physics 2025-08-01 Haimeng Zhao , Dong-Ling Deng

The wave-particle duality of light has led to two different encodings for optical quantum information processing. Several approaches have emerged based either on particle-like discrete-variable states, e.g. finite-dimensional quantum…

Quantum Physics · Physics 2014-07-04 Olivier Morin , Kun Huang , Jianli Liu , Hanna Le Jeannic , Claude Fabre , Julien Laurat

We propose a set of linear quantum entanglement witnesses constituted by local quantum-mechanical observables with each two possible measurement outcomes. These witnesses detect all the entangled resources which give rise to a better…

Quantum Physics · Physics 2012-05-04 Ming-Jing Zhao , Shao-Ming Fei , Xianqing Li-Jost

We present a fiber-based continuous-variable quantum key distribution system. In the scheme, a quantum signal of two non-orthogonal weak optical coherent states is sent through a fiber-based quantum channel. The receiver simultaneously…

We show that it is possible to transfer two-bit information via encoding a single qubit in a conventional nuclear magnetic resonance (NMR) experiment with two very weakly polarized nuclear spins. Nevertheless, the experiment can not be…

Quantum Physics · Physics 2007-05-23 Robabeh Rahimi , Kazuyuki Takeda , Masanao Ozawa , Masahiro Kitagawa

An entanglement witness is an observable detecting entanglement for a subset of states. We present a framework that makes an entanglement witness twice as powerful due to the general existence of a second (lower) bound, in addition to the…

Quantum Physics · Physics 2020-02-20 Joonwoo Bae , Dariusz Chruściński , Beatrix C. Hiesmayr