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The phenomenon of quantum entanglement marks one of the furthest departures from classical physics and is indispensable for quantum information processing. Despite its fundamental importance, the distribution of entanglement over long…

Quantum Physics · Physics 2021-07-27 Sebastian Ecker , Philipp Sohr , Lukas Bulla , Marcus Huber , Martin Bohmann , Rupert Ursin

It is shown that entanglement, which is a quantum correlation property of at least two subsystems, is imprinted in the mode structure of a single photon. The photon, which is emitted by two coupled cavities, carries the information on the…

Quantum Physics · Physics 2009-05-22 C. Di Fidio , W. Vogel

Photons offer the potential to carry large amounts of information in their spectral, spatial, and polarisation degrees of freedom. While state-of-the-art classical communication systems routinely aim to maximize this information-carrying…

We derive a general expression that quantifies the total entanglement production rate in continuous variable systems, where a source emits two entangled Gaussian beams with arbitrary correlators.This expression is especially useful for…

Quantum Physics · Physics 2016-08-03 Zhi Jiao Deng , Steven J. M. Habraken , Florian Marquardt

The quantification of quantum entanglement is a central issue in quantum information theory. Recently, Gao \emph{et al}. ( \href{http://dx.doi.org/10.1103/PhysRevLett.112.180501}{Phys. Rev. Lett. \textbf{112}, 180501 (2014)}) pointed out…

Quantum Physics · Physics 2021-05-11 Xianfei Qi , Ting Gao , Fengli Yan

Entangled photon pairs have been promised to deliver a substantial quantum advantage for two-photon absorption spectroscopy. However, recent work has challenged the previously reported magnitude of quantum enhancement in two-photon…

Using a spontaneous parametric-downconversion source of photon pairs, we are working towards the creation of arbitrary 2-qubit quantum states with high fidelity. Currently, all physically allowable combinations of polarization entanglement…

Quantum Physics · Physics 2007-05-23 Paul Kwiat , Joe Altepeter , David Branning , Evan Jeffrey , Nicholas Peters , Tzu-Chieh Wei

Quantum entanglement is one of the most prominent features of quantum mechanics and forms the basis of quantum information technologies. Here we present a novel method for the creation of quantum entanglement in multipartite and…

Quantum Physics · Physics 2017-02-24 Mario Krenn , Armin Hochrainer , Mayukh Lahiri , Anton Zeilinger

Particle entanglement is a fundamental resource upon which are based many quantum technologies. However, the up-to-now best sources of entangled photons rely on parametric down-conversion processes, which are optimal only at certain…

We address the experimental determination of entanglement for systems made of a pair of polarization qubits. We exploit quantum estimation theory to derive optimal estimators, which are then implemented to achieve ultimate bound to…

Quantum Physics · Physics 2015-05-27 G. Brida , I. P. Degiovanni , A. Florio , M. Genovese , P. Giorda , A. Meda , M. G. A. Paris , A. Shurupov

We study how entanglement in photoionization is transferred from an electron-ion pair to an electron-photon pair by fluorescence. Time-resolved von Neumann entropies are used to establish how information is shared between the particles.…

Quantum Physics · Physics 2025-08-18 Axel Stenquist , Jakob Nicolai Bruhnke , Felipe Zapata , Jan Marcus Dahlström

Exploiting photonic high-dimensional entanglement allows one to expand the bandwidth of quantum communication and information processing protocols through increased photon information capacity. However, the characterization of entanglement…

Quantum Physics · Physics 2017-10-20 Bienvenu Ndagano , Andrew Forbes

When a metastable state decays into radiation, there must be entanglement between the radiation and the decaying system, as well as between radiation collected at late and early times. We study the interplay between these two types of…

Quantum Physics · Physics 2026-04-13 Sergei Khlebnikov

Entanglement of formation is a fundamental measure that quantifies the entanglement of bipartite quantum states. This measure has recently been extended into multipartite states taking the name $\alpha$-entanglement of formation. In this…

Quantum Physics · Physics 2020-10-28 Sho Onoe , Spyros Tserkis , Austin P. Lund , Timothy C. Ralph

We demonstrate that any pure bipartite state of two qubits may be decomposed into a superposition of a maximally entangled state and an orthogonal factorizable one. Although there are many such decompositions, the weights of the two…

Quantum Physics · Physics 2009-11-07 Ayman F. Abouraddy , Bahaa E. A. Saleh , Alexander V. Sergienko , Malvin C. Teich

The newfound importance of ``entanglement as a resource'' in quantum computation and quantum communication compels us to quantify it in as many distinct ways as possible. Here we explore a new measure of entanglement for mixed quantum…

Quantum entanglement is an essential resource for quantum science and technology. However, entanglement detection and quantification, via typical entanglement measures such as linear entanglement entropy or negativity, can be a very…

Quantum Physics · Physics 2025-06-17 Diego Fallas Padilla , Mingjian Zhu , Han Pu

We introduce the concept of Shannon dimensionality D as a new way to quantify bipartite entanglement as measured in an experiment. This is applied to orbital-angular-momentum entanglement of two photons, using two state analyzers composed…

We address the problem of the persistence of entanglement of quantum light under mode transformations, where orthogonal modes define the parties between which quantum correlations can occur. Since the representation of a fixed photonic…

Quantum Physics · Physics 2019-12-30 Jan Sperling , Armando Perez-Leija , Kurt Busch , Christine Silberhorn

We investigate the entanglement properties of multi-mode Gaussian states, which have some symmetry with respect to the ordering of the modes. We show how the symmetry constraints the entanglement between two modes of the system. In…

Quantum Physics · Physics 2009-11-10 M. M. Wolf , F. Verstraete , J. I. Cirac