A quantum memory for orbital angular momentum photonic qubits

TL;DR

This paper demonstrates a quantum memory system capable of storing and retrieving orbital angular momentum-encoded photonic qubits with high fidelity, advancing quantum communication technologies utilizing this optical degree of freedom.

Contribution

It introduces a novel quantum memory for orbital angular momentum qubits, enabling on-demand storage and retrieval with quantum-level fidelity, a key step for quantum networks.

Findings

Fidelities exceeded classical benchmarks, confirming quantum storage.

Successfully stored and retrieved various OAM qubits.

Quantum tomography verified high-fidelity retrieval.

Abstract

Among the optical degrees of freedom, the orbital angular momentum of light provides unique properties, including mechanical torque action with applications for light manipulation, enhanced sensitivity in imaging techniques and potential high-density information coding for optical communication systems. Recent years have also seen a tremendous interest in exploiting orbital angular momentum at the single-photon level in quantum information technologies. In this endeavor, here we demonstrate the implementation of a quantum memory for quantum bits encoded in this optical degree of freedom. We generate various qubits with computer-controlled holograms, store and retrieve them on demand. We further analyse the retrieved states by quantum tomography and thereby demonstrate fidelities exceeding the classical benchmark, confirming the quantum functioning of our storage process. Our results provide an essential capability for future networks exploring the promises of orbital angular momentum of photons for quantum information applications.