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As a tutorial to the spatial aspects of Spontaneous Parametric Downconversion (SPDC), we present a detailed first-principles derivation of the transverse correlation width of photon pairs in degenerate collinear SPDC. This width defines the…

Quantum Physics · Physics 2018-03-01 James Schneeloch , John C. Howell

The use of optical clocks/oscillators in future ultra-precise navigation, gravitational sensing, coherent arrays, and relativity experiments will require time comparison and synchronization over terrestrial or satellite free-space links.…

Various quantum technology applications require high-purity single photons with high generation rate. Although different methods are employed to generate such photons, heralded single photons from spontaneous parametric down-conversion…

Quantum Physics · Physics 2022-07-15 A. Padhye , K. Muhammed Shafi , C. M. Chandrashekar

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…

This paper establishes a fundamental theory of secure clock synchronization. Accurate clock synchronization is the backbone of systems managing power distribution, financial transactions, telecommunication operations, database services,…

Cryptography and Security · Computer Science 2018-05-15 Lakshay Narula , Todd Humphreys

We present a method for precisely time-synchronizing the capture of image sequences from a collection of smartphone cameras connected over WiFi. Our method is entirely software-based, has only modest hardware requirements, and achieves an…

Computer Vision and Pattern Recognition · Computer Science 2019-08-16 Sameer Ansari , Neal Wadhwa , Rahul Garg , Jiawen Chen

We describe a cavity-enhanced spontaneous parametric down-conversion (CE-SPDC) source for narrowband photon pairs with filters such that over 97% of the correlated photons are in a single mode of 4.3(4) MHz bandwidth. Type-II phase…

Clock synchronization is ubiquitous in wireless systems for communication, sensing and control. In this paper we design a scalable system in which an indefinite number of passively receiving wireless units can synchronize to a single master…

Networking and Internet Architecture · Computer Science 2017-10-04 Dave Zachariah , Satyam Dwivedi , Peter Händel , Petre Stoica

The ability to determine the joint spectral properties of photon pairs produced by the processes of spontaneous parametric downconversion (SPDC) and spontaneous four wave mixing (SFWM) is crucial for guaranteeing the usability of heralded…

We report on a new technique for entanglement distillation of the bipartite continuous variable state of spatially correlated photons generated in the spontaneous parametric down-conversion process (SPDC), where tunable non-Gaussian…

Quantum Physics · Physics 2018-05-18 E. S. Gómez , P. Riquelme , M. A. Solis-Prosser , P. González , E. Ortega , G. B. Xavier , G. Lima

In spontaneous parametric down conversion (SPDC) based quantum information processing (QIP) experiments, there is a tradeoff between the coincide count rates (i.e. the pumping power of the SPDC), which limits the rate of the protocol, and…

Quantum Physics · Physics 2015-06-23 Masahiro Takeoka , Rui-Bo Jin , Masahide Sasaki

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

Quantum clock synchronization (QCS) aims to establish a shared temporal reference between distant nodes by exploiting uniquely quantum phenomena such as entanglement, single-photon interference, and quantum correlations. In contrast to…

Time synchronization is a crucial requirement in quantum key distribution (QKD)8 protocols, ensuring accurate key generation via the correct assignment of bits of raw key and9 enabling eavesdropping detection via the precise recording of…

Quantum Physics · Physics 2026-05-22 Lukas Tiefenthaler , Hannah Thiel , Davide Rusca , Antia Lamas Linares

For advanced quantum information technology, sources of photon pairs in quantum mechanically factorable states are of great importance for realizing high-fidelity photon-photon quantum gate operations. Here we experimentally demonstrate a…

Spontaneous downconversion is a versatile source for correlated biphotons that has been employed in many quantum sensing and imaging experiments. Spatially-resolved photon-counting detectors allow to access a large number of modes, posing…

Instrumentation and Detectors · Physics 2019-11-26 Ermes Toninelli , Paul-Antoine Moreau , Thomas Gregory , Miles J. Padgett

High-precision time synchronization is a vital prerequisite for many modern applications and technologies, including Smart Grids, Time-Sensitive Networking (TSN), and 5G networks. Although the Precision Time Protocol (PTP) can accomplish…

Cryptography and Security · Computer Science 2024-02-08 Andreas Finkenzeller , Oliver Butowski , Emanuel Regnath , Mohammad Hamad , Sebastian Steinhorst

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…

Fast and complete characterization of pulsed spontaneous parametric down conversion (SPDC) sources is important for applications in quantum information processing and communications. We propose a simple method to perform this task, which…

Photon sources based on spontaneous parametric down-conversion (SPDC) are central to experimental quantum optics and quantum technologies. Their performance is commonly quantified by three metrics: pair-collection probability, heralding…

Quantum Physics · Physics 2026-02-27 Carlos Sevilla-Gutiérrez , Varun Raj Kaipalath , Fabian Steinlechner