Heralded Generation of Ultrafast Single Photons in Pure Quantum States

TL;DR

This paper demonstrates a method to generate pure, indistinguishable single photons using spectrally engineered parametric downconversion sources, eliminating the need for spectral filtering and achieving high purity and interference visibility.

Contribution

It introduces a technique for controlling the modal structure of photon pairs to produce pure quantum states without spectral filters, advancing quantum photonics.

Findings

Achieved over 95% photon purity.

Generated indistinguishable photons with 94.4% raw Hong-Ou-Mandel visibility.

Eliminated spectral filters in multi-source interference schemes.

Abstract

We present an experimental demonstration of heralded single photons prepared in pure quantum states from a parametric downconversion source. It is shown that, through controlling the modal structure of the photon pair emission, one can generate pairs in factorable states and thence eliminate the need for spectral filters in multiple-source interference schemes. Indistinguishable heralded photons were generated in two independent spectrally engineered sources, and, by performing a Hong-Ou-Mandel interference between them without spectral filters at a raw visibility of 94.4%, their purity was measured to be over 95%.