L00L entanglement and the twisted quantum eraser

TL;DR

This paper demonstrates the generation of unbalanced two-photon entanglement in Laguerre-Gaussian modes and introduces a twisted quantum eraser to verify coherence, achieving high fidelity in the entangled states.

Contribution

It introduces a novel type of entanglement called $ ext{l}00 ext{l}$-entangled states in LG modes and demonstrates a twisted quantum eraser to verify two-photon coherence.

Findings

Generated states have fidelities of 95.31% and 89.80% to ideal states.

Successfully recovered Hong-Ou-Mandel interference with a twisted quantum eraser.

Demonstrated high-quality entanglement in LG mode space.

Abstract

We demonstrate the generation of unbalanced two-photon entanglement in the Laguerre-Gaussian (LG) transverse-spatial degree-of-freedom, where one photon carries a fundamental (Gauss) mode and the other a higher-order LG mode with a non-zero azimuthal ($\ell$) or radial ($p$) component. Taking a cue from the $N00N$ state nomenclature, we call these types of states $\ell 00 \ell$-entangled. They are generated by shifting one photon in the LG mode space and combining it with a second (initially uncorrelated) photon at a beamsplitter, followed by coincidence detection. In order to verify two-photon coherence, we demonstrate a two-photon ``twisted'' quantum eraser, where Hong-Ou-Mandel interference is recovered between two distinguishable photons by projecting them into a rotated LG superposition basis. Using an entanglement witness, we find that our generated states have fidelities of 95.31\% and 89.80\% to their respective ideal maximally entangled states. Besides being of fundamental interest, this type of entanglement will likely have a significant impact on tickling the average quantum physicist's funny bone.