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We report, for the first time, the generation of entangled photon pairs via type-0 spontaneous parametric down conversion in an ultra-thin wafer of lithium niobate in which momentum between the pump photon and daughter photons is not…

Quantum Physics · Physics 2020-01-08 C. Okoth , A Cavanna , T. Santiago-Cruz , M. V. Chekhova

We implement experimentally a method to generate photon-number$-$path and polarization entangled photon pairs using ``beamlike'' type-II spontaneous parametric down-conversion (SPDC), in which the signal-idler photon pairs are emitted as…

Quantum Physics · Physics 2009-11-10 Yoon-Ho Kim

Non-classical states of light, such as entangled photon pairs and number states, are essential for fundamental tests of quantum mechanics and optical quantum technologies. The most widespread technique for creating these quantum resources…

Quantum Physics · Physics 2010-07-30 H. Hübel , D. R. Hamel , A. Fedrizzi , S. Ramelow , K. J. Resch , T. Jennewein

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…

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…

Detailed investigations of single photon 1st-order interferences of separated emitters allow for analyzing the role of the mode function in quantum optics. In an earlier Young's double slit experiment using a higher spatial light mode some…

Quantum Physics · Physics 2015-01-06 Axel Heuer , Sebastian Raabe , Ralf Menzel

Entangled photon-pairs are a critical resource in quantum communication protocols ranging from quantum key distribution to teleportation. The current workhorse technique for producing photon-pairs is via spontaneous parametric down…

Stimulated parametric down-conversion (StimPDC) produces an idler beam that exhibits a phase conjugate of the spatial structure of the classical seed beam. Extending this effect to the single-photon regime can, in principle, enable the…

Spontaneous Parametric Down-Conversion (SPDC), also known as parametric fluorescence, parametric noise, parametric scattering and all various combinations of the abbreviation SPDC, is a non-linear optical process where a photon…

Quantum Physics · Physics 2018-09-12 Christophe Couteau

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

We explore the consequences of varying the pump beam waist that illuminates a nonlinear crystal, realizing spontaneous parametric down-conversion (SPDC). The coherence is transferred from the marginal one-photon wavefunction to the…

Quantum Physics · Physics 2024-11-07 Vikas S Bhat , Rounak Chatterjee , Kiran Bajar , Sushil Mujumdar

Spatial correlations of photon pairs from spontaneous parametric down-conversion (SPDC) underpin quantum imaging and entanglement certification. We present the first systematic study of spectral filter bandwidth effects on transverse…

Quantum Physics · Physics 2026-05-12 Hashir Kuniyil , Asad Ali , Saif Al-Kuwari

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

We present an optical design where polarization-entangled photon pairs are generated within two $\beta$-Barium Borate crystals whose optical axes are parallel. This design increases the spatial mode overlap of the emitted photon pairs…

Quantum Physics · Physics 2018-05-23 Aitor Villar , Alexander Lohrmann , Alexander Ling

The ability to engineer pairs of entangled photons is essential to quantum information science, and generating these states using spontaneous parametric down-conversion (SPDC) in nano- and micrometer-scale materials offers numerous…

Quantum Physics · Physics 2025-03-11 Nicholas J. Sorensen , Vitaliy Sultanov , Maria V. Chekhova

Generation of entangled photons through spontaneous parametric down-conversion (SPDC) from ultrasmall sources like thin films, metasurfaces, or nanoantennas, offers unprecedented freedom in quantum state engineering. However, as the source…

Quantum Physics · Physics 2024-02-28 Vitaliy Sultanov , Maria Chekhova

Optimizing the brightness of a spontaneous parametric down conversion (SPDC) source is an important task for many quantum information applications. We investigate the optimal focusing conditions to maximize the number of photons produced in…

Quantum Physics · Physics 2023-09-29 Lorenzo Coccia , Alberto Santamato , Giuseppe Vallone , Paolo Villoresi

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 paper the coherence and crossing symmetry of the electromagnetic interaction of photons involved in the spontaneous parametric down conversion (SPDC) phenomena in nonlinear crystals, are investigated. On this basis a new…

Quantum Physics · Physics 2008-10-23 D. B. Ion , P. Constantin , M. L. Ion

The ability to generate quantum entangled photon pairs through spontaneous parametric down conversion (SPDC) is playing a pivotal role in many applications in quantum technologies, including quantum communications, quantum computation, and…

Optics · Physics 2025-06-24 Tongmiao Fan , Jihua Zhang , Andrey A. Sukhorukov