Quantum information protocols in mixed qubit type registers of ¹³⁷Ba⁺ ions

Trapped barium ions are very well-suited to omg-style architectures [1] due to the long (∼ 30 s) lifetime of the metastable D_5/2 level. We present a system capable of controlling registers of ¹³⁷Ba⁺ ions utilising qubits encoded in both the ground and the metastable level. We achieve individual optical addressing with very low cross-talk within the ion chain via a fibre network coupled to a laser-written waveguide device [2].

We demonstrate full control over the different qubit types within ¹³⁷Ba⁺, facilitating the implementation of in-sequence dissipative operations on the ground level qubits, while maintaining the coherence of the metastable ones. These capabilities have allowed us to achieve extremely low SPAM errors for all three qubit types.

[1] D. T. C. Allcock et al. omg blueprint for trapped ion quantum computing with metastable states. Applied Physics Letters, 119(21):214002, 2021.

[2] A. S. Sotirova et al. Low Cross-Talk Optical Addressing of Trapped-Ion Qubits Using a Novel Integrated Photonic Chip, October 2023. arXiv:2310.13419.