Waveguided sources of consistent, single-temporal-mode squeezed light: the good, the bad, and the ugly

TL;DR

This paper analyzes how pump brightness affects the temporal mode structure of waveguided squeezed light sources, revealing trade-offs between indistinguishability and purity, and identifying the double pass configuration as optimal.

Contribution

It provides a theoretical comparison of different waveguided source configurations and their impact on the temporal mode quality of squeezed states.

Findings

Double pass configuration yields nearly indistinguishable states across brightness levels.

Filtering can restore indistinguishability but may reduce state purity.

Single pass configurations are less effective in maintaining indistinguishability.

Abstract

We study theoretically how the brightness of pumps, with fixed profiles, affects the temporal mode structure of squeezed states generated by fixed parametric waveguided sources. We find that the temporal modes of these squeezed states can be partially mismatched and thus distinguishable, which is undesirable when using these states as resources for quantum computing or heralded state generation. By studying common frequency filtering techniques used experimentally, we find that although one can regain indistinguishability it comes at the price of potentially greatly reducing the purity of the state. We consider three different source configurations: unapodized single pass, apodized single pass, and apodized double pass. We find that the double pass configuration produces optimal results with almost perfectly indistinguishable states over varying degrees of brightness.