High fidelity state preparation and measurement of ion hyperfine qubits with I > 1/2

TL;DR

This paper introduces a high-fidelity state preparation and measurement technique for ion hyperfine qubits with nuclear spins greater than 1/2, enabling broader isotope use in quantum computing.

Contribution

It develops a stroboscopic method combining optical pumping and microwave transitions for high-fidelity SPAM in higher nuclear spin isotopes.

Findings

Achieved a SPAM infidelity of approximately 9 x 10^-5.

Demonstrated the method with $^{137}$Ba$^+$ ion.

Facilitates use of more ion isotopes for quantum computing.

Abstract

We present a method for achieving high fidelity state preparation and measurement (SPAM) using trapped ion hyperfine qubits with nuclear spins higher than $I = 1/2$. The ground states of these higher nuclear spin isotopes do not afford a simple frequency-selective state preparation scheme. We circumvent this limitation by stroboscopically driving strong and weak transitions, blending fast optical pumping using dipole transitions and narrow microwave or optical quadrupole transitions. We demonstrate this method with the $I=3/2$ isotope $^{137}\mbox{Ba}^+$ to achieve a SPAM infidelity of $\left(9.0 \pm 1.3\right) \times 10^{-5}$ ($-40.5 \pm 0.6$ dB), facilitating the use of a wider range of ion isotopes with favorable wavelengths and masses for quantum computation.