Continuous variable multimode quantum states via symmetric group velocity matching

TL;DR

This paper demonstrates how symmetric group velocity matching in nonlinear waveguides can be used to engineer multimode continuous variable quantum states, advancing scalable quantum networks at telecommunications wavelengths.

Contribution

It introduces a novel approach to engineer multimode squeezed states using symmetric group velocity matching in waveguides, particularly focusing on type II PDC in KTP for quantum network applications.

Findings

Type II PDC in waveguides produces multiple squeezed modes.

Waveguide dimensions can be optimized for indistinguishability of signal and idler.

The approach is applicable to various nonlinear materials and wavelengths.

Abstract

Configurable and scalable continuous variable quantum networks for measurement-based quantum information protocols or multipartite quantum communication schemes can be obtained via parametric down conversion (PDC) in non-linear waveguides. In this work, we exploit symmetric group velocity matching (SGVM) to engineer the properties of the squeezed modes of the PDC. We identify type II PDC in a single waveguide as the best suited process, since multiple modes with non-negligible amount of squeezing can be obtained. We explore, for the first time, the waveguide dimensions, usually only set to ensure single-mode guiding, as an additional design parameter ensuring indistinguishability of the signal and idler fields. We investigate here potassium titanyl phosphate (KTP), which offers SGVM at telecommunications wavelengths, but our approach can be applied to any non-linear material and pump wavelength. This work paves the way towards the engineering of future large-scale quantum networks in the continuous variable regime.