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We make a source of entangled photons (SEP) using spontaneous parametric down-conversion (SPDC) in a non-linear crystal and study the spatial distribution of photon pairs obtained through the down-conversion of different modes of light…

We derive an exact formula for the angular Schmidt spectrum of the orbital angular momentum (OAM)-entangled states produced by parametric down-conversion (PDC). We show that our formula yields true theoretical spectrum without any…

Optics · Physics 2018-07-05 Girish Kulkarni , Lavanya Taneja , Shaurya Aarav , Anand K. Jha

In this work we provide a detailed theoretical and experimental analysis of the two-photon Orbital Angular Momentum (OAM) entangled state, generated by a type-I Spontaneous Parametric Down Conversion (SPDC) process, when decomposed in terms…

We show that the transfer of the angular spectrum of the pump beam to the two-photon state in spontaneous parametric down-conversion enables the generation of entangled Hermite-Gaussian modes. We derive an analytical expression for the…

Quantum Physics · Physics 2009-11-10 S. P. Walborn , S. Pádua , C. H. Monken

We measure the transverse entanglement of photon pairs on their propagation from the near to the far field of spontaneous parametric downconversion (SPDC). The Fedorov ratio, depending on the widths of conditional and unconditional…

Quantum Physics · Physics 2015-06-12 Felix Just , Andrea Cavanna , Maria V. Chekhova , Gerd Leuchs

Using the type-I SPDC process in BBO nonlinear crystal (NLC), we generate a polarization-entangled state near to the maximally-entangled Bell-state with high-visibility (high-brightness) $ 98.50 \pm 1.33 ~ \% $ ($ 87.71 \pm 4.45 ~ \% $) for…

Quantum Physics · Physics 2021-07-06 Ali Motazedifard , Seyed Ahmad Madani , N. S. Vayaghan

I investigate the properties of spontaneous parametric down-conversion (SPDC) involving co-linear Gaussian spatial modes for the pump and the photon collection optics. Approximate analytical and numerical results are obtained for the peak…

Quantum Physics · Physics 2010-11-10 Ryan S. Bennink

The first color photos of the parametric down-conversion (PDC) emission cone illustrate the correlation of longitudinal- and transverse momentum in the process, i.e., wavelength-dependent emission angle of PDC photons. However, current…

Photon pairs generated via spontaneous parametric down-conversion (SPDC) can exhibit entanglement in the Laguerre-Gaussian (LG) mode basis, which enables high-dimensional free-space quantum communication by exploiting the high-dimensional…

Quantum Physics · Physics 2025-07-03 Jungmo Lee , Kyungdeuk Park , Dongkyu Kim , Yonggi Jo , Dong-Gil Im , Yong Sup Ihn

A double-Gaussian model and the Schmidt modes are found for the biphoton wave function characterizing spontaneous parametric down-conversion with the degenerate collinear phase-matching of the type I and with a pulsed pump. The obtained…

Quantum Physics · Physics 2015-05-13 M. V. Fedorov , Yu. M. Mikhailova , P. A. Volkov

As known, the degree of entanglement of biphoton states with respect to the transverse components of photon wave vectors (momenta) or coordinates can be characterized either by the parameter K associated with the Schmidt decompositions, or…

Quantum Physics · Physics 2022-02-03 M. V. Fedorov , S. S. Mernova , K. V. Sliporod

The amount of entanglement that exists in a parametric down-converted state is investigated in terms of all the degrees of freedom of the state. We quantify the amount of entanglement by the Schmidt number of the state, represented as a…

Quantum Physics · Physics 2020-05-13 Filippus S. Roux

Stimulated emission tomography (SET) is an excellent tool for characterizing the process of spontaneous parametric down-conversion (SPDC), which is commonly used to create pairs of entangled photons for use in quantum information protocols.…

Quantum Physics · Physics 2024-07-04 Yang Xu , Saumya Choudhary , Robert W. Boyd

We show that the states generated by a three-mode spontaneous parametric downconversion (SPDC) interaction Hamiltonian possess tripartite entanglement of a different nature to other paradigmatic three-mode entangled states generated by the…

The purpose of this paper is to study entanglement of quantum states by means of Schmidt decomposition. The notion of Schmidt information which characterizes the non-randomness of correlations between two observers that conduct measurements…

Quantum Physics · Physics 2007-05-23 A. Yu. Bogdanov , Yu. I. Bogdanov , K. A. Valiev

We investigate entangled Schr\"odinger cat-like states (SCLSs) in degenerate and non-degenerate spontaneous parametric down-conversion (SPDC) with a fully quantized, depleted pump. Our fully quantum treatment, visualized via Wigner…

Quantum Physics · Physics 2026-04-03 Ranjit Singh , Alexander E. Teretenkov

We address the intrinsic multimode nature of the quantum state of light obtained by pulsed spontaneous parametric downconversion and develop a theoretical model based only on experimentally accessible quantities. We exploit the pairwise…

Quantum Physics · Physics 2010-11-17 A. Allevi , A. Andreoni , M. Bondani , F. A. Beduini , M. G. Genoni , S. Olivares , M. G. A. Paris

Scalable quantum photonics relies on interfacing many optical components under mutually compatible operating conditions. To that end, we demonstrate that spontaneous parametric down-conversion (SPDC) in nonlinear waveguides, a standard…

Entangled two-mode Gaussian states constitute an important building block for continuous variable quantum computing and communication protocols. In this work, we theoretically study two-mode bipartite states which are extracted from…

Quantum Physics · Physics 2026-01-21 Denis A. Kopylov , Torsten Meier , Polina R. Sharapova

We provide a general decomposition of the two-photon state produced by spontaneous parametric down-conversion in Hermite-Gaussian modes, in the case that the pump beam is described by a Hermite-Gaussian beam of any order. We show that the…

Quantum Physics · Physics 2012-08-22 S. P. Walborn , A. H. Pimentel