# Quasiphasematched concurrent nonlinearities in periodically poled KTiOPO_4 for quantum computing over the optical frequency comb

## TL;DR

This paper demonstrates the design and experimental realization of a multigrating periodically poled KTiOPO_4 crystal that enables three coincident nonlinear interactions, advancing the development of scalable quantum computing using optical frequency combs.

## Contribution

It introduces a novel multigrating periodically poled crystal supporting multiple nonlinear interactions simultaneously for quantum computing applications.

## Key findings

- Successfully achieved three coincident nonlinear interactions in a single crystal.
- Enabled second harmonic generation at 780 nm from 1560 nm pump.
- Paved the way for scalable quantum computing with optical frequency combs.

## Abstract

We report the successful design and experimental implementation of three coincident nonlinear interactions, namely ZZZ ("type-0"), ZYY (type-I), and YYZ/YZY (type-II) second harmonic generation of 780 nm light from a 1560 nm pump beam in a single, multigrating, periodically poled KTiOPO_4 crystal. The resulting nonlinear medium is the key component for making a scalable quantum computer over the optical frequency comb of a single optical parametric oscillator.