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Generating nonclassical states of photons such as polarization entangled states on a monolithic chip is a crucial step towards practical applications of optical quantum information processing such as quantum computing and quantum key…

Quantum Physics · Physics 2021-12-30 Dongpeng Kang , Minseok Kim , Haoyu He , Amr S. Helmy

The aim of this review paper is to enlighten some recent progresses in quantum optical metrology in the part of quantum efficiency measurements of photo-detectors performed with bi-photon states. The intrinsic correlated nature of entangled…

Quantum Physics · Physics 2015-06-26 G. Brida , M. Genovese , M. Gramegna

A workflow for evaluation of entanglement source quality is proposed. Based on quantum state density matrices obtained from theoretical models and experimental data, we make an estimate of a potential performance of a quantum entanglement…

Quantum Physics · Physics 2021-04-27 Radim Hošák , Ivo Straka , Ana Predojević , Radim Filip , Miroslav Ježek

The generation of high-quality entangled photon pairs has been being a long-sought goal in modern quantum communication and computation. To date, the most widely-used entangled photon pairs are generated from spontaneous parametric…

Heralded single photon sources are often implemented using spontaneous parametric downconversion, but their quality can be restricted by optical loss, double pair emission and detector dark counts. Here, we show that the performance of such…

Quantum Physics · Physics 2018-05-23 Patrick F. Poitras , Evan Meyer-Scott , Deny R. Hamel

A simple experimental setup consisting of a spontaneous parametric down-conversion source and passive linear optics is proposed for conditional preparation of a maximally entangled polarization state of two photons. Successful preparation…

Quantum Physics · Physics 2009-11-07 C. Sliwa , K. Banaszek

Spontaneous Parametric Down Conversion (SPDC) holds a pivotal role in quantum physics, facilitating the creation of entangled photon pairs, heralded single photons and squeezed light, critical resources for many applications in quantum…

Quantum Physics · Physics 2026-01-06 Muhammad Erew , Yuval Reches , Ofir Yesharim , Moshe Goldstein , Ady Arie , Haim Suchowski

Single photons are an important prerequisite for a broad spectrum of quantum optical applications. We experimentally demonstrate a heralded single-photon source based on spontaneous parametric down-conversion in collinear bulk optics, and…

Distributing entangled states over potentially long distances provides a key resource for many protocols in quantum communication and quantum cryptography. Ideally, this should be implemented in a heralded manner. By starting with four…

Quantum Physics · Physics 2024-06-19 Francis Marcellino , Patrik Caspar , Tiff Brydges , Hugo Zbinden , Rob Thew

Coincidence-count discrimination have turned utterly practical in the characterization of photon-pair processes and heralded single photons. Here, we implement a heralded single photon source based on parametric down-conversion (PDC) in a…

Quantum Physics · Physics 2025-12-22 Daniel Borrero Landazabal , Kaisa Laiho

High-rate entanglement generation is essential for the realization of practical quantum repeaters. To this end, frequency multiplexing of the photons employed is an effective approach. In particular, schemes using cavity-enhanced…

Quantum Physics · Physics 2026-04-02 Ryoma Komatsudaira , Tomoyuki Horikiri

Entangled states of photons form the foundation of quantum communication, computation, and metrology. Yet their generation remains fundamentally constrained: in the absence of intrinsic photon-photon interactions, the generation of such…

We study implementing a heralded single-photon source with second-order nonlinear photonic crystals. Injecting pump and signal light beams into a one-dimensional photonic crystal composed of a material with a large second-order nonlinear…

Quantum Physics · Physics 2025-07-25 Hiroo Azuma

We propose a heralded entanglement generation scheme based on Gaussian sources enhanced by photon addition and subtraction operations. By combining single-mode squeezing, linear interferometers, and conditional photon-number measurements on…

Quantum Physics · Physics 2026-04-17 Yun-Long Cao , Xiao-Ye Xu , Chuan-Feng Li , Guang-Can Guo

The nonlinear optical process of spontaneous parametric down-conversion (SPDC) is widely studied for applications in quantum information science due to its ability to produce two photons that can be entangled in many degrees of freedom. For…

Quantum Physics · Physics 2014-10-06 Hannah E. Guilbert , Daniel J. Gauthier

The generation of entangled photons through Spontaneous Parametric Down-Conversion (SPDC) is a critical resource for many key experiments and technologies in the domain of quantum optics. Historically, SPDC was limited to the generation of…

Two-photon states generated from spontaneous parametric down-conversion (SPDC) can display entanglement in all degrees of freedom (DoFs) of light, including spatial, temporal, and polarization. The coupling between different DoFs of a…

We present a detailed study on the properties of single photons generated by spontaneous parametric down conversion (SPDC) when both the spectral and spatial degrees of freedom are controlled by means of filters. Our results show that it is…

Quantum Physics · Physics 2018-01-19 Jefferson Flórez , Omar Calderón , Clara I. Osorio , Alejandra Valencia

An on-demand single-photon source is a fundamental building block in quantum science and technology. We experimentally demonstrate the proof of concept for a scheme to generate on-demand single photons via actively multiplexing several…

Quantum Physics · Physics 2013-05-29 Xiao-song Ma , Stefan Zotter , Johannes Kofler , Thomas Jennewein , Anton Zeilinger

We describe a method to detect twin-beam multiphoton entanglement based on a beam splitter and weak nonlinearities. For the twin-beam four-photon entanglement, we explore a symmetry detector. It works not only for collecting two-pair…

Quantum Physics · Physics 2020-08-04 Yingqiu He , Dong Ding , Fengli Yan , Ting Gao