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We numerically and experimentally show that all photons generated by spontaneous parametric down-conversion (SPDC) follow a transverse amplitude similar to that of the pump. This amplitude transfer from pump to SPDC is revealed in the…

Quantum Physics · Physics 2018-04-04 Ali Anwar , Pravin Vaity , Chithrabhanu Perumangatt , R. P. Singh

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

The temporal response of single-photon detectors is usually obtained by measuring their impulse response to short-pulsed laser sources. In this work, we present an alternative approach using time-correlated photon pairs generated in…

Quantum Physics · Physics 2021-01-25 Lijiong Shen , Jianwei Lee , Antony Winata Hartanto , Pengkian Tan , Christian Kurtsiefer

Quantum Key Distribution (QKD) allows unconditionally secure communication based on the laws of quantum mechanics rather then assumptions about computational hardness. Optimizing the operation parameters of a given QKD implementation is…

The practical prospect of quantum communication and information processing relies on sophisticated single photon pairs which feature controllable waveform, narrow spectrum, excellent purity, fiber compatibility and miniaturized design. For…

Direct spectral characterization of a quantum photon-pair source usually involves cumbersome, costly, and time-consuming detection issues. In this study, we experimentally characterize the spectral properties of a type-II phase-matched…

In this paper, we study the possible parametric down conversion processes in a periodically poled customized Lithium Niobate (LiNbO3) ridge waveguide. Our analysis of spontaneous parametric down-conversion (SPDC), first, with a Gaussian…

Optics · Physics 2019-06-26 Ramesh Kumar , Joyee Ghosh

We address the question of the implementation of long-distance device-independent quantum key distribution (DI QKD) by proposing two experimentally viable schemes. Those schemes only use spontaneous parametric down-conversion (SPDC) sources…

The photon statistics of Spontaneous Parametric Down Conversion (SPDC) exhibit dependencies on wavelength, pump power, and coincidence time. Notably, the average photon numbers were found to asymmetrically increase with increasing pump…

Quantum Physics · Physics 2026-05-01 Jeffrey Carvalho , Chiran Wijesundara , Tim Thomay

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 theoretically analyze the feasibility of entanglement-based quantum key distribution (QKD) protocols considering widely used spontaneous parametric down-conversion (SPDC) and novel quantum dot (QD) sources. We account for multiphoton…

Quantum Physics · Physics 2025-10-24 Mariia Gumberidze , Vladyslav C. Usenko

A new method for generating entangled photons with controllable frequency correlation via spontaneous parametric down-conversion (SPDC) is presented. The method entails initiating counter-propagating SPDC in a single-mode nonlinear…

Quantum key distribution (QKD) using entangled photon sources (EPS) is a cornerstone of secure communication. Despite rapid advances in QKD, conventional protocols still employ beam splitters (BSs) for passive random basis selection.…

Quantum Physics · Physics 2026-03-02 Ayan Kumar Nai , Gopal Prasad Sahu , Rutuj Gharate , C. M. Chandrashekar , G. K. Samanta

We performed a second-order spontaneous parametric down-conversion (SPDC) experiment in a Type II phase-matched KTiOPO4 crystal pumped at 532 nm giving birth to a signal beam at 1037 nm and an idler one at 1092 nm along the x-axis of the…

Quantum Physics · Physics 2025-02-10 Julien Bertrand , Véronique Boutou , Benoît Boulanger

We address the problem of efficient modelling of photon pairs generated in spontaneous parametric down-conversion and coupled into single-mode fibers. It is shown that when the range of relevant transverse wave vectors is restricted by the…

Quantum Physics · Physics 2009-09-08 Piotr Kolenderski , Wojciech Wasilewski , Konrad Banaszek

This paper reports a novel single mode source of narrow-band entangled photon pairs at telecom wavelengths under continuous wave excitation, based on parametric down conversion. For only 7 mW of pump power it has a created spectral radiance…

Quantum Physics · Physics 2008-02-19 Matthaeus Halder , Alexios Beveratos , Rob T Thew , Corentin Jorel , Hugo Zbinden , Nicolas Gisin

We propose a novel, physically-constrained and differentiable approach for the generation of D-dimensional qudit states via spontaneous parametric down-conversion (SPDC) in quantum optics. We circumvent any limitations imposed by the…

Entanglement distribution is at the heart of most quantum communication protocols. Inevitable loss of photons along quantum channels is a major obstacle for distributing entangled photons over long distances, as the no-cloning theorem…

High-efficient and high-purity photon sources are highly desired for quantum information processing. We report the design of a chip-scale hybrid SixNy and thin film periodically-poled lithium niobate waveguide for generating high-purity…

Quantum photonic technologies rely on the ability to generate, manipulate, and interfere indistinguishable single photons on a scalable platform. Among the various approaches, spontaneous parametric down-conversion (SPDC) remains one of the…

Quantum Physics · Physics 2026-03-03 Jost Kellner , Alessandra Sabatti , Tristan Kuttner , Robert J. Chapman , Rachel Grange