# Temporally versatile polarization entanglement from Bragg-reflection waveguides

## TL;DR

This paper explores how controlling the temporal delay in broadband PDC from Bragg-reflection waveguides allows for tunable polarization entanglement coherence, providing insights for direct source engineering.

## Contribution

It demonstrates a method to modify the coherence of polarization entanglement by adjusting temporal delay, enhancing control over entangled photon states.

## Key findings

- Ability to tune entanglement coherence via temporal delay
- Insight into engineering entangled states at the source
- Potential for on-chip polarization entanglement control

## Abstract

Bragg-reflection waveguides emitting broadband parametric down-conversion (PDC) have been proven to be well suited for the on-chip generation of polarization entanglement in a straightforward fashion [R. T. Horn et al., Sci. Rep. 3, 2314 (2013)]. Here, we investigate how the properties of the created states can be modified by controlling the relative temporal delay between the pair of photons created via PDC. Our results offer an easily accessible approach for changing the coherence of the polarization entanglement, in other words, to tune the phase of the off-diagonal elements of the density matrix. Furthermore, we provide valuable insight in the engineering of these states directly at the source.