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We present the convergence study of a recurrence entanglement purification protocol using arbitrary two-qubit initial states. The protocol is based on a rank two projector in the Bell basis which serves as a two-qubit operation replacing…

Quantum Physics · Physics 2016-11-23 Juan Mauricio Torres , József Zsolt Bernád

We generalize previously proposed conditions each measure of entanglement has to satisfy. We present a class of entanglement measures that satisfy these conditions and show that the Quantum Relative Entropy and Bures Metric generate two…

Quantum Physics · Physics 2011-07-19 V. Vedral , M. B. Plenio

In recent work, Akers et al. proved that the entanglement of purification $E_p(A:B)$ is bounded below by half of the $q$-R\'enyi reflected entropy $S_R^{(q)}(A:B)$ for all $q\geq2$, showing that $E_p(A:B) = \frac{1}{2} S_R^{(q)}(A:B)$ for a…

Quantum Physics · Physics 2024-02-23 Josiah Couch , Phuc Nguyen , Sarah Racz , Georgios Stratis , Yuxuan Zhang

The field of quantum communications promises the faithful distribution of quantum information, quantum entanglement, and absolutely secret keys, however, the highest rates of these tasks are fundamentally limited by the transmission…

Quantum Physics · Physics 2022-11-18 Matthew S. Winnel , Joshua J. Guanzon , Nedasadat Hosseinidehaj , Timothy C. Ralph

One of the fundamental concepts of quantum information theory is that of entanglement purification; that is, the transformation of a partially entangled state into a smaller-dimensional, more completely entangled state. Of particular…

Quantum Physics · Physics 2008-02-03 Eric M. Rains

Entanglement routing establishes remote entanglement connection between two arbitrary nodes, which is one of the most important functions in quantum networks. The existing routing mechanisms mainly improve the robustness and throughput…

Quantum Physics · Physics 2022-06-23 Jian Li , Mingjun Wang , Qidong Jia , Kaiping Xue , Nenghai Yu , Qibin Sun , Jun Lu

A key question for most applications involving reconfigurable linear wave systems is how accurately a desired linear operator can be realized by configuring the system's tunable elements. The relevance of this question spans from…

Signal Processing · Electrical Eng. & Systems 2026-02-17 Philipp del Hougne

Consider entanglement concentration schemes that convert n identical copies of a pure state into a maximally entangled state of a desired size with success probability being close to one in the asymptotic limit. We give the distillable…

Quantum Physics · Physics 2009-11-07 Masahito Hayashi , Masato Koashi , Keiji Matsumoto , Fumiaki Morikoshi , Andreas Winter

A purification scheme which utilizes the action of repeated measurements on a (part of a total) quantum system is briefly reviewed and is applied to a few simple systems to show how it enables us to extract an entangled state as a target…

Quantum Physics · Physics 2007-05-23 Hiromichi Nakazato , Makoto Unoki , Kazuya Yuasa

Quantum communication enables secure information transmission and entanglement distribution, but these tasks are fundamentally limited by the capacities of quantum channels. While quantum repeaters can mitigate losses and noise,…

Quantum Physics · Physics 2026-02-02 Ozlem Erkilic , Matthew S. Winnel , Aritra Das , Sebastian Kish , Ping Koy Lam , Jie Zhao , Syed M. Assad

We derive necessary and sufficient conditions for the approximate correctability of a quantum code, generalizing the Knill-Laflamme conditions for exact error correction. Our measure of success of the recovery operation is the worst-case…

Quantum Physics · Physics 2010-03-25 Cédric Bény , Ognyan Oreshkov

We show that there exists a gap between the performance of separable and collective measurements in qubit mixed-state estimation that persists in the large sample limit. We characterize such gap in terms of the corresponding bounds on the…

Quantum Physics · Physics 2009-11-11 E. Bagan , M. A. Ballester , R. D. Gill , R. Munoz-Tapia , O. Romero-Isart

Quantum Entanglement is a fundamentally important resource in Quantum Information Science; however, generating it in practice is plagued by noise and decoherence, limiting its utility. Entanglement distillation and forward error correction…

Quantum Physics · Physics 2023-07-14 Vaishnavi L. Addala , Shu Ge , Stefan Krastanov

We give a detailed description of the entanglement purification protocol which generates maximally entangled states with high efficiencies from realistic Gaussian continuous variable entangled states. The physical implementation of this…

Quantum Physics · Physics 2009-11-06 Lu-Ming Duan , G. Giedke , J. I. Cirac , P. Zoller

In this paper, we place bounds on when it is impossible to purify a noisy two-qubit state if all the gates used in the purification protocol are subject to adversarial local, independent, noise. It is found that the gate operations must be…

Quantum Physics · Physics 2008-05-20 Alastair Kay

Entanglement purification allows the creation of qubit pairs of arbitrarily high fidelity with respect to a maximally entangled state, starting from a larger number of low-fidelity pairs. Purification requires quantum memory, a role for…

Quantum Physics · Physics 2016-01-20 Adrian Auer , Guido Burkard

Randomized measurements access nonlinear functionals without full tomography, yet turning third-order local single-copy data into a strong entanglement test remains difficult. We convert the reduction criterion into an experimentally…

Quantum Physics · Physics 2026-04-16 Giovanni Scala , Gniewomir Sarbicki

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 distribution is a core mechanism for the future quantum Internet. The quantum world is, however, a faulty environment. Hence, successful entanglement swapping is error-prone. The occurrence of quantum state errors can be…

Quantum Physics · Physics 2023-02-28 Michel Barbeau , Joaquin Garcia-Alfaro , Evangelos Kranakis

The tight, in a sense, lower estimates of diamond-norm distance from a given quantum channel to the sets of degradable, antidegradable and entanglement-breaking channels are obtained via the tight continuity bounds for quantum mutual…

Quantum Physics · Physics 2019-10-18 M. E. Shirokov , A. V. Bulinski