Ion-Photon Entanglement via the 6D3 / 2 state in Ba+

A dual species Yb+/Ba+ ion trap is used to create entanglement between memory spin qubits and photonic qubits. The flying qubits are emitted via the 6S_{1 / 2} < - > 6P_{1 / 2} transition in Ba138+. In previous work the atoms were excited on this same 493 nm transition. However, it is advantageous to excite the atom on the 6D_{3 / 2} < - > 6P_{1 / 2} transition at 650 nm, while still collecting 493 nm photons. This removes the excitation light as a source of noise and reduces double excitation errors. Most significantly, the D < - > P transition allows us to use a slower excitation, such that instead of requiring a picosecond pulsed laser, we can gate a CW laser using nanosecond in-fiber EO interferometers that do not exist at shorter wavelengths. However, the increased multiplicity of the D state manifold is a challenge for state initialization and readout. We present our solutions to these challenges, and subsequent ion-photon entanglement using this new toolbox.

This work is supported by the ARO with funding from the IARPA LogiQ program, the AFOSR, the ARO MURI on Modular Quantum Circuits, the AFOSR MURI on Quantum Transduction, and the ARL Center for Distributed Quantum Information.