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Entanglement is defined between subsystems of a quantum system, and at fixed time two regions of space can be viewed as two subsystems of a relativistic quantum field. The entropy of entanglement between such subsystems is ill-defined…

Quantum Physics · Physics 2014-10-01 Issam Ibnouhsein , Fabio Costa , Alexei Grinbaum

Resource identification and quantification is an essential element of both classical and quantum information theory. Entanglement is one of these resources, arising when quantum communication and nonlocal operations are expensive to…

Quantum Physics · Physics 2013-03-20 Sebastian Meznaric

Algebraic approach to quantum non - separability is applied to the case of two qubits. It is based on the partition of the algebra of observables into independent subalgebras and the tensor product structure of the Hilbert space is not…

Quantum Physics · Physics 2015-05-30 L. Derkacz , M. Gwozdz , L. Jakobczyk

Assessing the quality of an ensemble of noisy entangled states is a central task in quantum information processing. Usually this is done by measuring and hence destroying multiple copies, from which state tomography or fidelity estimation…

Quantum Physics · Physics 2023-02-14 Ferran Riera-Sàbat , Jorge Miguel-Ramiro , Wolfgang Dür

Localizability of entanglement in fully inseparable states is a key ingredient of assisted quantum information protocols as well as measurement-based models of quantum computing. We investigate the existence of fully inseparable states with…

Quantum Physics · Physics 2017-10-31 M. Mičuda , D. Koutný , M. Miková , I. Straka , M. Ježek , L. Mišta

We investigate the properties of three entanglement measures that quantify the statistical distinguishability of a given state with the closest disentangled state that has the same reductions as the primary state. In particular, we…

Quantum Physics · Physics 2009-11-07 J. Eisert , K. Audenaert , M. B. Plenio

Non-linear properties of quantum states, such as entropy or entanglement, quantify important physical resources and are frequently used in quantum information science. They are usually calculated from a full description of a quantum state,…

Quantum states are represented by positive semidefinite Hermitian operators with unit trace, known as density matrices. An important subset of quantum states is that of separable states, the complement of which is the subset of…

Mathematical Physics · Physics 2020-12-04 Grigoriy Blekherman , H. M. Bharath

We introduce a technique for applying quantum expanders in a distributed fashion, and use it to solve two basic questions: testing whether a bipartite quantum state shared by two parties is the maximally entangled state and disproving a…

Quantum Physics · Physics 2015-01-26 Dorit Aharonov , Aram W. Harrow , Zeph Landau , Daniel Nagaj , Mario Szegedy , Umesh Vazirani

Quantum theory makes the most accurate empirical predictions and yet it lacks simple, comprehensible physical principles from which the theory can be uniquely derived. A broad class of probabilistic theories exist which all share some…

Quantum Physics · Physics 2012-04-17 Borivoje Dakic , Caslav Brukner

Production of quantum states exhibiting a high degree of entanglement out of noisy conditions is one of the main goals of quantum information science. Here, we provide a conditional yet efficient entanglement distillation method which…

Given $n$ copies of an unknown quantum state $\rho\in\mathbb{C}^{d\times d}$, quantum state certification is the task of determining whether $\rho=\rho_0$ or $\|\rho-\rho_0\|_1>\varepsilon$, where $\rho_0$ is a known reference state. We…

Quantum Physics · Physics 2024-01-19 Yuhan Liu , Jayadev Acharya

Quantum steering describes the phenomenon that one system can be immediately influenced by another with local measurements. It can be detected by the violation of a powerful and useful steering criterion from general entropic uncertainty…

Quantum Physics · Physics 2020-02-26 Huan Yang , Zhi-Yong Ding , Dong Wang , Hao Yuan , Xue-Ke Song , Jie Yang , Chang-Jin Zhang , Liu Ye

We present a new technique to reduce the expected number of measurements to declare an unknown quantum state as entangled. Our method is based on the geometric criterion and so requires only local Pauli measurements. Using concentration of…

Quantum Physics · Physics 2017-09-13 Bingjie Wang , Stephen Brierley

We present a framework for certifying entanglement properties of quantum states and measurements in line networks. The framework is based on the generalised Choi isomorphism, which can be used to map bipartite states and measurements into…

Quantum Physics · Physics 2025-06-13 Sophie Egelhaaf , Roope Uola

Multipartite entanglement has been widely regarded as key resources in distributed quantum computing, for instance, multi-party cryptography, measurement based quantum computing, quantum algorithms. It also plays a fundamental role in…

Quantum Physics · Physics 2020-09-23 Nengkun Yu

The concept of entanglement is at the core of the theory of quantum information. In this paper a criterion for unentanglement of quantum states is proposed and proved. This criterion is natural, practical and easy to check.

Quantum Physics · Physics 2023-12-21 Xufeng Liu

We address a problem of identifying a given pure state with one of two reference pure states, when no classical knowledge on the reference states is given, but a certain number of copies of them are available. We assume the input state is…

Quantum Physics · Physics 2009-11-11 A. Hayashi , M. Horibe , T. Hashimoto

We introduce the entangled coherent state representation, which provides a powerful technique for efficiently and elegantly describing and analyzing quantum optics sources and detectors while respecting the photon number superselection rule…

Quantum Physics · Physics 2007-05-23 Barry C. Sanders , Stephen D. Bartlett , Terry Rudolph , Peter L. Knight

Quantum entanglement is a fundamental property of quantum mechanics and plays a crucial role in quantum computation and information. We study entanglement via the lens of computational complexity by considering quantum generalizations of…

Quantum Physics · Physics 2024-03-01 Fernando Granha Jeronimo , Pei Wu