Towards 780 nm Ion-Photon entanglement

Trapped ions excel as networking nodes due to long-lived internal states for local processing and readily accessible ion-photon entanglement. Practical implementation of multi-node quantum networks will likely include different types of quantum technologies with links enabled by quantum frequency conversion.  Previously, we demonstrated ion/neutral atom-based hybrid platforms in the form of slow light [1] and two-photon interference between these two different node-types over a 150 m fiber network [2]. These experiments, however, used photons originating from a 138Ba+ trapped ion without measurement of the ion-photon entanglement required in quantum networking protocols [3]. Here, we present our progress on measuring the entanglement between an ion and frequency converted photons at 780 nm.  We demonstrate control and detection of ground state and optical qubits and use this as part of a protocol to measure ion-photon entanglement fidelity at both the native ion emission wavelength of 493 nm and the frequency converted wavelength at 780 nm.

 

[1] Siverns, J. D., et al. Science Advances 5 (10), eaav4651 (2019)

[2] Craddock, A. N., et al. Phys. Rev. Lett. 123 (21), 213601 (2019)

[3] Stephenson, L. J., et al. Phys. Rev. Lett. 124.11  110501 (2020)