Scalable fiber integrated source for higher-dimensional path-entangled photonic quNits

TL;DR

This paper introduces a fiber-integrated, scalable source for generating high-quality, higher-dimensional path-entangled photonic quNits in the telecom band, enabling advanced quantum optical experiments with integrated photonics.

Contribution

The authors present a novel fiber-based source for higher-dimensional entangled photons that is scalable and compatible with on-chip path encoding, demonstrated with a high-fidelity two-qubit state.

Findings

Achieved a background-corrected fidelity of 99.45% for the entangled state

Demonstrated a method to extend the source to higher dimensions

Validated the source's scalability and compatibility with integrated photonics

Abstract

Integrated photonic circuits offer the possibility for complex quantum optical experiments in higher-dimensional photonic systems. However, the advantages of integration and scalability can only be fully utilized with the availability of a source for higher-dimensional entangled photons. Here, a novel fiber integrated source for path-entangled photons in the telecom band at 1.55\mum using only standard fiber technology is presented. Due to the special design the source shows good scalability towards higher-dimensional entangled photonic states (quNits), while path entanglement offers direct compatibility with on-chip path encoding. We present an experimental realization of a path-entangled two-qubit source. A very high quality of entanglement is verified by various measurements, i.a. a tomographic state reconstruction is performed leading to a background corrected fidelity of (99.45+-0.06)%. Moreover, we describe an easy method for extending our source to arbitrarily high dimensions.