Polarization control of single photon quantum orbital angular momentum states

TL;DR

This paper demonstrates experimental schemes using q-plates to coherently transfer and control single photon orbital angular momentum states, enabling access to higher-order subspaces with high fidelity for quantum information applications.

Contribution

The paper introduces and experimentally validates optical schemes utilizing q-plates for efficient polarization-to-orbital angular momentum transfer in single photons, including access to higher-order states.

Findings

Successful control of orbital angular momentum within |m|=2 and |m|=4 subspaces

Schemes are reliable, efficient, and high fidelity

Enables manipulation of high-dimensional quantum states

Abstract

The orbital angular momentum of photons, being defined in an infinitely dimensional discrete Hilbert space, offers a promising resource for high-dimensional quantum information protocols in quantum optics. The biggest obstacle to its wider use is presently represented by the limited set of tools available for its control and manipulation. Here, we introduce and test experimentally a series of simple optical schemes for the coherent transfer of quantum information from the polarization to the orbital angular momentum of single photons and vice versa. All our schemes exploit a newly developed optical device, the so-called "q-plate", which enables the manipulation of the photon orbital angular momentum driven by the polarization degree of freedom. By stacking several q-plates in a suitable sequence, one can also access to higher-order angular momentum subspaces. In particular, we demonstrate the control of the orbital angular momentum $m$ degree of freedom within the subspaces of $|m|=2 \hbar$ and $|m|=4\hbar$ per photon. Our experiments prove that these schemes are reliable, efficient and have a high fidelity.