# Polarization diversity phase modulator for measuring frequency-bin entanglement of a biphoton frequency comb in a depolarized channel

## TL;DR

This paper introduces a polarization diversity phase modulator that enables polarization-independent measurement of frequency-bin entanglement in biphoton pairs, facilitating quantum communication in depolarized channels.

## Contribution

The authors develop a polarization diversity scheme for phase modulation, allowing measurement of frequency-bin entanglement regardless of photon polarization, advancing quantum networking capabilities.

## Key findings

- Successfully demonstrated polarization-independent phase modulation
- Enabled measurement of frequency-bin entanglement in depolarized channels
- Facilitated potential applications in quantum networking and Bell state discrimination

## Abstract

Phase modulation has emerged as a technique to create and manipulate high-dimensional frequency-bin entanglement. A necessary step to extending this technique to depolarized channels, such as those in a quantum networking environment, is the ability to perform phase modulation independent of photon polarization. This also necessary to harness hypertanglement in the polarization and frequency degrees of freedom for operations like Bell state discrimination. However, practical phase modulators are generally sensitive to the polarization of light and this makes them unsuited to such applications. We overcome this limitation by implementing a polarization diversity scheme to measure frequency-bin entanglement in arbitrarily polarized photon pairs.