Recovering the full dimensionality of hyperentanglement in collinear photon pairs

TL;DR

This paper proposes a simple interference setup to recover the full dimensionality of collinear hyperentangled photon pairs, enabling efficient high-dimensional quantum information processing without post-selection.

Contribution

It introduces a phase-condition-based interference method to fully recover hyperentanglement in collinear photon pairs, overcoming limitations of spatial mode restrictions.

Findings

The method can recover full hyperentanglement dimensionality.

It does not require post-selection, increasing efficiency.

The approach is feasible for generating high-dimensional entangled photons.

Abstract

Exploiting hyperentanglement of photon pairs, that is, simultaneous entanglement in multiple degrees of freedom(DOFs), increases the dimensionality of Hilbert spaces for quantum information processing. However, generation of hyperentangled photon pairs collinearlly, while produces high brightness, results in a smaller Hilbert space due to the two photons being in the same spatial mode. In this letter, we point out that one can recover the full dimensionality of such hyperentanglement through a simple interference set up, similar to the time-reversed Hong-Ou-Mandel (TR-HOM) process. Different from the standard TR-HOM, we point out a critical phase condition has to be satisfied in order to recover the hyperentanglement. We theoretically analyze the realization of this approach and discuss the feasibility of generating truly hyperentangled photon pairs. Our proposed approach does not require post-selection and hence enables efficient hyper-entangled photon pairs generation for high-dimensional quantum applications.