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We explicate conditions under which, the two magnon state becomes highly entangled and is useful for several quantum communication protocols. This state, which is experimentally realizable in quantum dots using Heisenberg exchange…

We present a family of three-qubit quantum states with a basic local hidden variable model. Any von Neumann measurement can be described by a local model for these states. We show that some of these states are genuine three-partite…

Quantum Physics · Physics 2007-05-23 Geza Toth , Antonio Acin

In entanglement theory, there are different methods to consider one state being more entangled than another. The "maximally" entangled states in a multipartite system can be defined from an axiomatic perspective. According to different…

Quantum Physics · Physics 2025-03-13 Yanwen Liang , Fengli Yan , Ting Gao

We derive a hierarchy of continuous-variable multipartite entanglement conditions in terms of second-order moments of position and momentum operators that generalizes existing criteria. Each condition corresponds to a convex optimization…

Quantum Physics · Physics 2015-11-04 E. Shchukin , P. van Loock

We propose a scheme for continuous-variable telecloning with phase-conjugate inputs (PCI). Two cases of PCI telecloning are considered. The first case is where PCI telecloning produces $M$ clones nonlocally and $M$ anticlones locally, or…

Quantum Physics · Physics 2009-11-13 Jing Zhang , Changde Xie , Kunchi Peng , Peter van Loock

Encoding quantum information in continuous variables (CV)---as the quadrature of electromagnetic fields---is a powerful approach to quantum information science and technology. CV entanglement---light beams in Einstein-Podolsky-Rosen (EPR)…

A quantum key distribution (QKD) system must fulfill the requirement of universal composability to ensure that any cryptographic application (using the QKD system) is also secure. Furthermore, the theoretical proof responsible for security…

We consider continuous-variable quantum key distribution with discrete-alphabet encodings. In particular, we study protocols where information is encoded in the phase of displaced coherent (or thermal) states, even though the results can be…

Quantum Physics · Physics 2021-01-18 Panagiotis Papanastasiou , Stefano Pirandola

Genuine entanglement is the strongest form of multipartite entanglement. Genuinely entangled pure states contain entanglement in every bipartition and as such can be regarded as a valuable resource in the protocols of quantum information…

Quantum Physics · Physics 2021-12-07 K. V. Antipin

We propose a deterministic scheme of generating genuine multiparty entangled states in quantum networks of arbitrary size having various geometric structures -- we refer to it as entanglement circulation. The procedure involves optimization…

Quantum Physics · Physics 2022-09-16 Pritam Halder , Ratul Banerjee , Srijon Ghosh , Amit Kumar Pal , Aditi Sen De

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

The need for secrecy and security is essential in communication. Secret sharing is a conventional protocol to distribute a secret message to a group of parties, who cannot access it individually but need to cooperate in order to decode it.…

Quantum Physics · Physics 2017-01-16 Ioannis Kogias , Yu Xiang , Qiongyi He , Gerardo Adesso

Continuous-Variable (CV) devices are a promising platform for demonstrating large-scale quantum information protocols. In this framework, we define a general quantum computational model based on a CV hardware. It consists of vacuum input…

Quantum Physics · Physics 2019-02-06 Tom Douce , Damian Markham , Elham Kashefi , Peter van Loock , Giulia Ferrini

Entangling two systems at distant locations using a {\it separable} mediating ancilla is a counterintuitive phenomenon proposed for qubits by T. Cubitt {\it et al}. [Phys. Rev. Lett. {\bf 91}, 037902 (2003)]. We show that such entanglement…

Quantum Physics · Physics 2012-08-27 Ladislav Mišta, , Natalia Korolkova

Continuous-variable (CV) quantum computing offers a promising framework for scalable quantum machine learning, leveraging optical systems with infinite-dimensional Hilbert spaces. While discrete-variable (DV) quantum neural networks have…

Quantum Physics · Physics 2025-11-05 Daniel Alejandro Lopez , Oscar Montiel , Oscar Castillo , Miguel Lopez-Montiel

We introduce a homology-based technique for the analysis of multiqubit state vectors. In our approach, we associate state vectors to data sets by introducing a metric-like measure in terms of bipartite entanglement, and investigate the…

Quantum Physics · Physics 2020-03-25 Riccardo Mengoni , Alessandra DI Pierro , Laleh Memarzadeh , Stefano Mancini

Entanglement is a unique nature of quantum theory and has tremendous potential for application. Nevertheless, the complexity of quantum entanglement grows exponentially with an increase in the number of entangled particles. Here we…

Quantum Physics · Physics 2018-01-17 S. M. Zangi , Jun-Li Li , Cong-Feng Qiao

Starting from arbitrary Hilbert spaces, we reduce the problem to verify entanglement of any bipartite quantum state to finite dimensional subspaces. Hence, entanglement is a finite dimensional property. A generalization for multipartite…

Quantum Physics · Physics 2015-05-13 J. Sperling , W. Vogel

Large-scale quantum networks have been employed to overcome practical constraints on transmission and storage for single entangled systems. The deterministic preparation of entangled states is one of the key factors for realization of…

Quantum Physics · Physics 2025-11-07 Shuanping Du , Zhaofang Bai

Continuous-variable (CV) codes and their application in quantum communication have attracted increasing attention. In particular, one typical CV codes, cat-codes, has already been experimentally created using trapped atoms in cavities with…

Quantum Physics · Physics 2025-07-08 Pei-Zhe Li , William J. Munro , Kae Nemoto , Nicoló Lo Piparo