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The notion of entanglement of quantum states is usually defined with respect to a fixed bipartition. Indeed, a global basis change can always map an entangled state to a separable one. The situation is however different when considering a…

Quantum Physics · Physics 2021-06-02 Yu Cai , Baichu Yu , Pooja Jayachandran , Nicolas Brunner , Valerio Scarani , Jean-Daniel Bancal

Entangled quantum states are regarded as a key resource in quantum key distribution (QKD) protocols. However, quantum correlations, other than entanglement can also play a significant role in the QKD protocols. In this work, we will focus…

Quantum Physics · Physics 2025-12-09 Rashi Jain , Satyabrata Adhikari

Many protocols and experiments in quantum information science are described in terms of simple measurements on qubits. However, in a real implementation, the exact description is more difficult, and more complicated observables are used.…

Quantum Physics · Physics 2010-09-28 Tobias Moroder , Otfried Gühne , Normand J. Beaudry , Marco Piani , Norbert Lütkenhaus

We study a protocol in which many parties use quantum communication to transfer a shared state to a receiver without communicating with each other. This protocol is a multiparty version of the fully quantum Slepian-Wolf protocol for two…

Quantum Physics · Physics 2012-07-06 David Avis , Patrick Hayden , Ivan Savov

Entanglement [1, 2] enables powerful new quantum technologies [3-8], but in real-world implementations, entangled states are often subject to decoherence and preparation errors. Entanglement distillation [9, 10] can often counteract these…

Quantum Physics · Physics 2010-09-24 Jonathan Lavoie , Rainer Kaltenbaek , Marco Piani , Kevin J. Resch

Quantum entanglement plays crucial roles in quantum information processing. Quantum entangled states have become the key ingredient in the rapidly expanding field of quantum information science. Although the nonclassical nature of…

Quantum Physics · Physics 2010-12-22 Ming Li , Shao-Ming Fei , Xianqing Li-Jost

Entanglement plays a crucial role in quantum information protocols, thus the dynamical behavior of entangled states is of a great importance. In this paper we suggest a useful scheme that permits a direct measure of entanglement in a…

Quantum Physics · Physics 2011-07-04 Smail Bougouffa , Awatif Hindi

We discuss the problem of characterizing upper bounds on entanglement in a bipartite quantum system when only the reduced density matrices (marginals) are known. In particular, starting from the known two-qubit case, we propose a family of…

The notion of distillable entanglement is one of the fundamental concepts of quantum information theory. Unfortunately, there is an apparent mismatch between the intuitive and rigorous definitions of distillable entanglement. To be precise,…

Quantum Physics · Physics 2009-10-31 Eric M. Rains

Quantum entanglement is at the heart of many tasks in quantum information. Apart from simple cases (low dimensions, few particles, pure states), however, the mathematical structure of entanglement is not yet fully understood. This tutorial…

Quantum Physics · Physics 2015-06-26 Dagmar Bruss

The degree to which a pure quantum state is entangled can be characterized by the distance or angle to the nearest unentangled state. This geometric measure of entanglement is explored for bi-partite and multi-partite pure and mixed states.…

Quantum Physics · Physics 2009-05-18 Tzu-Chieh Wei

Provable entanglement has been shown to be a necessary precondition for unconditionally secure key generation in the context of quantum cryptographic protocols. We estimate the maximal threshold disturbance up to which the two legitimate…

Quantum Physics · Physics 2007-05-23 G. M. Nikolopoulos , A. Khalique , G. Alber

Quantum Internet relies on quantum entanglement as a fundamental resource for secure and efficient quantum communication, reshaping data transmission. In this context, entanglement distillation emerges as a crucial process that plays a…

Quantum Physics · Physics 2024-07-30 Chengkai Zhu , Chenghong Zhu , Xin Wang

We study the fully entangled fraction of quantum states. An upper bound is obtained for arbitrary dimensional bipartite systems. This bound is shown to be exact for the case of two-qubit systems. An inequality related the fully entangled…

Quantum Physics · Physics 2009-11-13 Ming Li , Shao-Ming Fei , Zhi-Xi Wang

We present here an overview of our work concerning entanglement properties of composite quantum systems. The characterization of entanglement, i.e. the possibility to assert if a given quantum state is entangled with others and how much…

Quantum Physics · Physics 2007-05-23 K. Eckert , O. Gühne , F. Hulpke , P. Hyllus , J. Korbicz , J. Mompart , D. Bruß , M. Lewenstein , A. Sanpera

Multipartite entanglement is a valuable resource for quantum technologies. However, detecting this resource can be challenging: for genuine multipartite entanglement, the detection may require global measurements that are hard to implement…

Quantum Physics · Physics 2024-11-22 Fei Shi , Lin Chen , Giulio Chiribella , Qi Zhao

One of the most sought-after goals in experimental quantum communication is the implementation of a quantum repeater. The performance of quantum repeaters can be assessed by comparing the attained rate with the quantum and private capacity…

Quantum Physics · Physics 2016-06-27 Kenneth Goodenough , David Elkouss , Stephanie Wehner

Device-independent quantum key distribution (DIQKD) is one of the most challenging tasks in quantum cryptography. The protocols and their security are based on the existence of Bell inequalities and the ability to violate them by measuring…

Quantum Physics · Physics 2025-06-09 Rotem Arnon , Felix Leditzky

The Schmidt coefficients capture all entanglement properties of a pure bipartite state and therefore determine its usefulness for quantum information processing. While the quantification of the corresponding properties in mixed states is…

Quantum Physics · Physics 2019-04-08 Gael Sentís , Christopher Eltschka , Otfried Gühne , Marcus Huber , Jens Siewert

This paper defines the fidelity of recovery of a quantum state on systems $A$, $B$, and $C$ as a measure of how well one can recover the full state on all three systems if system $A$ is lost and a recovery operation is performed on system…

Quantum Physics · Physics 2015-11-23 Kaushik P. Seshadreesan , Mark M. Wilde