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Spontaneous parametric down conversion (SPDC) has been largely exploited as a tool for absolute calibration of photon-counting detectors, i.e detectors registering very small photon fluxes. In [J. Opt. Soc. Am. B 23, 2185 (2006)] we derived…

Quantum Physics · Physics 2009-11-13 Giorgio Brida , Maria Chekhova , Marco Genovese , Ivano Ruo-Berchera

Spontaneous parametric down-conversion (SPDC) is the most widely used process for generating entangled photon pairs. In SPDC, a pump photon interacts with a nonlinear optical crystal and splits into two entangled photons called the signal…

Spontaneous parametric down conversion (SPDC) has proven to be a robust and prominent method for creating non-classical light sources of entangled single-photon pairs. However, such sources suffer from low efficiency due to the inherent…

Optics · Physics 2025-08-27 Sky Semone , Matthew J. Brandsema , Christos Argyropoulos

Quantum entanglement, the non-separability of a multipartite wave function, became essential in understanding the non-locality of quantum mechanics. In optics, this non-locality can be demonstrated on impressively large length scales, as…

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…

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 directly observe far-field correlations of x-ray photon pairs generated by spontaneous parametric down-conversion (SPDC). Using an energy-resolved, two-dimensional photon counting detector we record the full ring-shaped emission of both…

We analyze the process of photon-pair generation via spontaneous parametric down-conversion in a quadratic nonlinear asymmetric waveguide coupler. The two waveguides have different geometry, such that light coupling only occurs within a…

Optics · Physics 2019-11-13 Philip B. Main , Peter J. Mosley , Andrey V. Gorbach

We show that an optical vortex beam, implemented classically, can be transferred to the transverse amplitude of a heralded single photon. For this purpose we have relied on the process of spontaneous parametric downconversion (SPDC) for the…

Quantum imaging, which harnesses quantum correlations to achieve imaging with multiple advantages over classical optics, has been in development for several years. Here, we explore sunlight, serving as the pump beam, to excite spontaneous…

Quantum Physics · Physics 2026-05-22 Ye Xing , Deifei Xu , Yuan Li , Wuhong Zhang , Lixiang Chen

We experimentally demonstrate a violation of local realism with highly spatially multimode polarization-entangled two-photon states produced by spontaneous parametric down-conversion (SPDC) pumped by a spatially incoherent light source-a…

Quantum Physics · Physics 2025-12-01 Cheng Li , Jeremy Upham , Boris Braverman , Robert W. Boyd

Entanglement generated by Spontaneous Parametric Down Conversion (SPDC) involves multiple, often mutually correlated degrees of freedom. These degrees of freedom are often treated independently, overlooking the intrinsic correlation between…

Quantum Physics · Physics 2026-03-06 F. Crislane V. de Brito , Sylwia Kolenderska , Piotr Kolenderski

Two-photon states generated through degenerate spontaneous parametric down-conversion (SPDC) can exhibit sharp correlations in the transverse spatial coordinates. This property leads to unique free-space propagation features. Here, we show…

Quantum Physics · Physics 2025-05-20 Nazanin Dehghan , Alessio D'Errico , Yingwen Zhang , Benjamin Sussman , Ebrahim Karimi

Spontaneous parametric down-conversion (SPDC) has shown great promise in the generation of pure and indistinguishable single photons. Photon pairs produced in bulk crystals are highly correlated in terms of transverse space and frequency.…

Quantum Physics · Physics 2023-08-21 Baghdasar Baghdasaryan , Fabian Steinlechner , Stephan Fritzsche

The requirement on the symmetry of the biphoton wave function results in a double peak structure of the coincidence spectra of Spontaneous Parametric Down Conversion (SPDC) [1]. In this work we report the experimental observation of this…

Quantum Physics · Physics 2013-01-04 Dmitry A. Kalashnikov , Mikhail V. Fedorov , Leonid A. Krivitsky

In this work we study the transverse spatial correlation of the pair of photons generated via the process of spontaneous parametric frequency down-conversion, in periodically poled non-linear crystals illuminated by a pulsed laser beam. It…

Quantum Physics · Physics 2009-06-26 O. Cosme , A. Delgado , G. Lima , C. H. Monken , S. Pádua

We propose a method for directly producing radially and azimuthally polarized photon pairs through spontaneous parametric downconversion (SPDC). This method constitutes a novel geometry for SPDC, in which a radially polarized Bessel-Gauss…

Quantum Physics · Physics 2016-10-14 Rebecca Y. Saaltink , Lambert Giner , Robert W. Boyd , Ebrahim Karimi , Jeff S. Lundeen

Spontaneous parametric downconversion is the primary source to generate entangled photon pairs in quantum photonics laboratories. Depending on the experimental design, the generated photon pairs can be correlated in the frequency spectrum,…

Quantum Physics · Physics 2021-05-19 Alessio D'Errico , Felix Hufnagel , Filippo Miatto , Mohammadreza Rezaee , Ebrahim Karimi

High flux of hyperentangled photons entails collecting the two-photon emission over relatively wide extent in frequency and transverse space within which the photon pairs are simultaneously entangled in multiple degrees of freedom. In this…

Quantum Physics · Physics 2017-04-05 Salem F. Hegazy , Jala El-Azab , Yehia A. Badr , Salah S. A. Obayya

In this letter, we study spontaneous parametric down-conversion (SPDC) in a periodically poled structure composed of two linearly uncoupled resonators that are nonlinearly coupled via a Mach-Zehnder interferometer. The device does not…

Optics · Physics 2024-06-27 Alessia Stefano , Luca Zatti , Marco Liscidini