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A Macro-state consisting of N= 3.5 x 10^4 photons in a quantum superposition and entangled with a far apart single-photon state (Micro-state) is generated. Precisely, an entangled photon pair is created by a nonlinear optical process, then…

Quantum Physics · Physics 2009-11-13 Francesco De Martini , Fabio Sciarrino , Chiara Vitelli

We consider the quantum field theory for a scalar model of the electromagnetic field interacting with a system of two-level atoms. In this setting, we show that it is possible to uniquely determine the density of atoms from measurements of…

Analysis of PDEs · Mathematics 2026-02-03 Matti Lassas , Medet Nursultanov , Lauri Oksanen , John C. Schotland

Cold atomic ensembles can mediate the generation of entanglement between pairs of photons. Photons with specific directions of propagation are detected, and the entanglement can reside in any of the degrees of freedom that describe the…

Quantum Physics · Physics 2009-11-13 Clara I. Osorio , Sergio Barreiro , Morgan W. Mitchell , Juan P. Torres

Purely azimuthal entanglement is analyzed for noncollinear frequency-degenerate biphoton states. The degree of azimuthal entanglement is found to be very high, with the Schmidt parameter $K$ on the order of the ratio of the pump waist to…

Quantum Physics · Physics 2016-03-23 M. V. Fedorov

Semiconductor quantum dots are among the best sources of on-demand entangled photon pairs. The degree of entanglement, however, is generally limited by the fine structure splitting of exciton states. In this paper, we theoretically…

Quantum Physics · Physics 2023-12-27 Mukesh Kumar Samal , Divya Mishra , Parvendra Kumar

A model of single photon detection, illustrated by a photon-absorbing superfluid or superconducting microvolume, is formulated as a cascading pair of quantum phase transitions. In the first, the microvolume transitions to the normal state…

Quantum Physics · Physics 2019-12-19 Peter B. Weichman

It is shown that bipartition of optical solitons can be used to generate entangled light beams. The achievable amount of entanglement can be substantially larger for N-bound solitons N=2,3 than for the fundamental soliton (N=1). An analysis…

Quantum Physics · Physics 2009-11-06 Eduard Schmidt , Ludwig Knoll , Dirk-Gunnar Welsch

We investigate how entanglement can enhance two-photon absorption in a three-level system. First, we employ the Schmidt decomposition to determine the entanglement properties of the optimal two-photon state to drive such a transition, and…

Quantum Physics · Physics 2021-10-29 Edoardo G Carnio , Andreas Buchleitner , Frank Schlawin

Entangled pairs of microwave photons are commonly produced in the narrow frequency band of a resonator, which represents a modified vacuum density of states. We use a broadband, semi-infinite transmission line terminated by a…

Quantum Physics · Physics 2020-04-16 B. H. Schneider , A. Bengtsson , I. M. Svensson , T. Aref , G. Johansson , Jonas Bylander , P. Delsing

I conjecture that only those states of light whose Wigner function is positive are real states, and give arguments suggesting that this is not a serious restriction. Hence it follows that the Wigner formalism in quantum optics is capable of…

Quantum Physics · Physics 2007-05-23 Emilio Santos

First, we show how the quantum circuits for generating and measuring multi-party entanglement of qubits can be translated to continuous quantum variables. We derive sufficient inseparability criteria for $N$-party continuous-variable states…

Quantum Physics · Physics 2007-05-23 Peter van Loock , Samuel L. Braunstein

We report on the experimental generation of an entangled state with a spectrally pure heralded single-photon state and a weak coherent state. By choosing group-velocity matching in the nonlinear crystal, our system for producing entangled…

Entangled photons produced by spontaneous parametric down-conversion have been of paramount importance for our current understanding of quantum mechanics and advances in quantum information. In this process, the quantum correlations of the…

Quantum Physics · Physics 2020-11-11 Lucas Hutter , Gustavo Lima , Stephen P. Walborn

Nonlinear processes of light scattering on a two-level system near resonance are considered. The problem is reduced to the emission and absorption of an entangled system, formed by a strong resonant field and a two-level system, having a…

Quantum Physics · Physics 2009-10-31 M. L. Ter-Mikayelyan

Numerous inequalities involving moments of integrated intensities and revealing nonclassicality and entanglement in bipartite optical fields are derived using the majorization theory, non-negative polynomials, the matrix approach, as well…

Quantum Physics · Physics 2018-12-11 Jan Perina , Ievgen I. Arkhipov , Vaclav Michalek , Ondrej Haderka

An accessible tabletop source for the production of entangled x rays is crucial for the field of high-energy quantum optics. Here, we present a detailed analysis of the entanglement and polarization of the two photons emitted by an electron…

Quantum Physics · Physics 2024-11-01 T. D. C. de Vos , J. J. Postema , B. H. Schaap , A. Di Piazza , O. J. Luiten

Photon antibunching in the light scattered by single quantum emitters is one of the hallmarks of quantum optics, providing an unequivocal demonstration of the quantized nature of the electromagnetic field. Antibunching can be intuitively…

Quantum Physics · Physics 2017-02-03 Luigi Garziano , Alessandro Ridolfo , Simone De Liberato , Salvatore Savasta

The pairwise entanglement of an arbitrary atomic pair randomly extracted from a laser-driven dense multiqubit sample in the presence of quantum dissipation due to spontaneous emission is considered. The dipole-dipole interaction between the…

Quantum Physics · Physics 2015-05-14 M. Macovei , J. Evers , C. H. Keitel

Duality in the entanglement of identical particles manifests that entanglement in only one variable can be revealed at a time. We demonstrate this using polarization and orbital angular momentum (OAM) variables of indistinguishable photons…

Quantum Physics · Physics 2025-11-20 Nijil Lal , Sarika Mishra , Anju Rani , Anindya Banerji , Chithrabhanu Perumangattu , R. P. Singh

We prove experimentally the predicted existence of a three-qubit quantum state with genuine multipartite entanglement which can be certified solely from its separable two-qubit reduced density matrices. The qubits are encoded into different…

Quantum Physics · Physics 2020-08-05 Michal Mičuda , Robert Stárek , Jan Provazník , Olga Leskovjanová , Ladislav Mišta,