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Bell's theorem shows that local measurements on entangled states give rise to correlations incompatible with local hidden variable models. The degree of quantum nonlocality is not maximal though, as there are even more nonlocal theories…

Quantum Physics · Physics 2018-12-26 Cristhiano Duarte , Samuraí Brito , Barbara Amaral , Rafael Chaves

Many-qubit entanglement is crucial for quantum information processing although its exploitation is hindered by the detrimental effects of the environment surrounding the many-qubit system. It is thus of importance to study the dynamics of…

Quantum Physics · Physics 2015-12-08 P. Espoukeh , R. Rahimi , S. Salimi , P. Pedram

We show that the quantum Fisher information provides a sufficient condition to recognize multi-particle entanglement in a $N$ qubit state. The same criterion gives a necessary and sufficient condition for sub shot-noise phase sensitivity in…

Quantum Physics · Physics 2015-05-13 L. Pezze' , A. Smerzi

Entanglement-assisted quantum communication employs pre-shared entanglement between sender and receiver as a resource. We apply the same framework to quantum metrology, introducing shared entanglement between the preparation and the…

Quantum Physics · Physics 2016-07-06 Zixin Huang , Chiara Macchiavello , Lorenzo Maccone

We consider graph states of arbitrary number of particles undergoing generic decoherence. We present methods to obtain lower and upper bounds for the system's entanglement in terms of that of considerably smaller subsystems. For an…

Quantum Physics · Physics 2009-07-15 Daniel Cavalcanti , Rafael Chaves , Leandro Aolita , Luiz Davidovich , Antonio Acin

We explore the advantages of a class of entanglement criteria for continuous variable systems based on the Husimi $Q$-distribution in scenarios with sparse experimental data. The generality of these criteria allows optimizing them for a…

Quantum Physics · Physics 2024-01-17 Martin Gärttner , Tobias Haas , Johannes Noll

Being able to implement effective entanglement distribution in noisy environments is a key step towards practical quantum communication, and long-term efforts have been made on the development of it. Recently, it has been found that the…

Quantum Physics · Physics 2016-04-14 Xin-Wen Wang , Sixia Yu , Deng-Yu Zhang , C. H. Oh

We propose two semi-device-independent approaches that are able to quantify unknown multipartite quantum entanglement experimentally, where the only information that has to be known beforehand is quantum dimension, and the concept that…

Quantum Physics · Physics 2022-01-05 Lijinzhi Lin , Zhaohui Wei

We provide an explicit example of a Bell inequality with 3 settings and 2 outcomes per site for which the largest violation is not obtained by the maximally entangled state, even if its dimension is allowed to be arbitrarily large. This…

Quantum Physics · Physics 2013-05-29 Thomas Vidick , Stephanie Wehner

Given the goal of maximizing CHSH violation, we compare the optimal strategies of entanglement and nonlocality distillation. In the limit of the number of copies of the shared state, entanglement distillation is guaranteed to work by…

Quantum Physics · Physics 2026-03-03 Peter Høyer , Jibran Rashid , Razeen ud Din

Due to the anisotropy of quantum lossy channels one must choose optimal bases of input states for best estimating them. In this paper, we obtain that the equal probability Schr\"{o}dinger cat states are optimal for estimating a single lossy…

Quantum Physics · Physics 2007-05-23 Xian-Ting Liang

In an entanglement swapping scenario, if two sources sharing entangled states between three parties are independent, local correlations lead to a different kind of inequalities than the standard Bell inequalities, known as network local…

Quantum Physics · Physics 2022-11-23 Pritam Halder , Ratul Banerjee , Shiladitya Mal , Aditi Sen De

We introduce a new aspect of nonlocality which arises when the task of quantum states distinguishability is considered under local operations and shared entanglement in the absence of classical communication. We find the optimal amount of…

Quantum Physics · Physics 2016-03-24 Berry Groisman , Sergii Strelchuk

Quantum steering, loosely speaking the distribution of entanglement from an untrusted party, is a form of quantum nonlocality which is intermediate between entanglement and Bell nonlocality. Determining which states can be steered is…

Quantum Physics · Physics 2013-03-06 Nicolas Brunner , Daniel Cavalcanti

This paper considers a sequential sensor scheduling and remote estimation problem with multiple communication channels. Departing from the classical remote estimation paradigm, which involves one communication channel (noiseless or noisy),…

Systems and Control · Computer Science 2018-04-10 Xiaobin Gao , Emrah Akyol , Tamer Basar

Starting from several copies of bipartite noisy entangled states, we design a global and optimal local measurement-based protocol in one- and two-dimensional lattices by which any two or more prefix sites can be connected via entanglement.…

Quantum Physics · Physics 2021-01-04 Ratul Banerjee , Srijon Ghosh , Shiladitya Mal , Aditi Sen De

The single-letter characterisation of the entanglement-assisted capacity of a quantum channel is one of the seminal results of quantum information theory. In this paper, we consider a modified communication scenario in which the receiver is…

Quantum Physics · Physics 2024-09-16 Kaiyuan Ji , Bartosz Regula , Mark M. Wilde

Sharing entanglement across quantum interconnects is fundamental for quantum information processing. We discuss a practical setting where this interconnect, modeled by a quantum channel, is used once with the aim of sharing high fidelity…

Quantum Physics · Physics 2023-10-09 Vikesh Siddhu , John Smolin

We present an effcient experimental procedure that certifies non vanishing quantum capacities for qubit noisy channels. Our method is based on the use of a fixed bipartite entangled state, where the system qubit is sent to the channel…

For quantum states of two subsystems, entanglement measures are related to capacities of communication tasks -- highly entangled states give higher capacity of transmitting classical as well as quantum information. However, we show that…

Quantum Physics · Physics 2010-02-05 Aditi Sen De , Ujjwal Sen