Experimental filtering of two-, four-, and six-photon singlets from single PDC source

TL;DR

This paper demonstrates a stable, high-contrast method for generating invariant multi-photon entangled states from a single PDC source using filtering, avoiding interferometric overlaps, with potential for quantum information applications.

Contribution

It introduces a filtering technique to produce multi-photon invariant entangled states from a single source without interferometers, leveraging bosonic enhancement.

Findings

Successfully generated 2-, 4-, and 6-photon invariant entangled states

Achieved high interference contrast and stable setup

Potential for quantum information protocol demonstrations

Abstract

Invariant entangled states remain unchanged under simultaneous identical unitary transformations of all their subsystems. We experimentally generate and characterize such invariant two-, four-, and six-photon polarization entangled states. This is done only with a suitable filtering procedure of multiple emissions of entangled photon pairs from a single source, without any interferometric overlaps. We get the desired states utilizing bosonic emission enhancement due to indistinguishability. The setup is very stable, and gives high interference contrasts. Thus, the process is a very likely candidate for various photonic demonstrations of quantum information protocols.