Generation of fully phase controlled two-photon entangled states

TL;DR

This paper demonstrates a method to generate fully phase-controlled two-photon entangled states using a single trapped calcium ion coupled to an optical cavity, achieving high fidelity and precise phase control.

Contribution

It introduces a resource-efficient scheme for generating two-photon entanglement with full phase control using a single ion-cavity system.

Findings

Achieved two-photon entangled states with up to 82% fidelity.

Demonstrated full phase control over the entangled states.

Utilized a single $^{40}$Ca$^+$ ion for efficient resource use.

Abstract

Control over the internal states of trapped ions makes them the ideal system to generate single and two-photon states. Coupling a single ion to an optical cavity enables efficient emission of single photons into a single spatial mode and grants control over their temporal shape, phase and frequency. Using the long coherence time of the ion's internal states and employing a scheme to protect the coherence of the ion-cavity interaction, we demonstrate the generation of a two-photon entangled state with full control over the phase. Initially, ion-photon entanglement is generated. A second photon is subsequently generated, mapping the ion's state onto the second photon. By adjusting the drive field the phase of the entangled state can be fully controlled. We implement this scheme in the most resource efficient way by utilizing a single $^{40}$Ca$^+$ ion coupled to an optical cavity and demonstrate the generation of a two-photon entangled stated with full phase control with a fidelity of up to 82\%.