Spontaneous parametric down-conversion

TL;DR

This paper explains the physics and applications of Spontaneous Parametric Down-Conversion (SPDC), a nonlinear optical process crucial for quantum optics experiments, highlighting its quantum nature and experimental uses.

Contribution

It provides a foundational overview of SPDC's physics and applications, serving as an introductory resource for students and researchers in quantum optics.

Findings

SPDC involves a photon splitting into two lower-energy photons.

SPDC is essential for quantum cryptography, simulation, and metrology.

The paper highlights the quantum properties and experimental applications of SPDC.

Abstract

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 spontaneously splits into two other photons of lower energies. One would think that this article is about particle physics and yet it is not, as this process can occur fairly easily on a day to day basis in an optics laboratory. Nowadays, SPDC is at the heart of many quantum optics experiments for applications in quantum cryptography, quantum simulation, quantum metrology but also for testing fundamentals laws of physics in quantum mechanics. In this article, we will focus on the physics of this process and highlight few important properties of SPDC. There will be two parts: a first theoretical one showing the particular quantum nature of SPDC and the second part, more experimental and in particular focusing on applications of parametric down-conversion. This is clearly a non-exhaustive article about parametric down-conversion as there is a tremendous literature on the subject, but it gives the necessary first elements needed for a novice student or researcher to work on SPDC sources of light.