Curator's Take
This research introduces yttrium ions as a promising new candidate for trapped-ion quantum computing, potentially offering significant advantages over the current workhorses like calcium and ytterbium ions. The key innovation lies in yttrium's unique electronic structure that combines a nuclear-spin qubit for robust information storage with multiple accessible energy levels that could enable more sophisticated quantum operations while reducing crosstalk between qubits. What makes this particularly exciting is that the researchers conducted both experimental spectroscopy and theoretical calculations to fully characterize the ion's properties, providing a complete roadmap for implementing yttrium-based quantum computers. If successfully developed, this platform could help address some of the major scaling challenges in trapped-ion systems by offering better isolation of quantum operations and more flexible control schemes.
— Mark Eatherly
Summary
Engineering large-scale quantum computers which simultaneously provide high-fidelity quantum operations, low memory errors, low crosstalk, and reasonable resource usage remains an outstanding challenge across quantum computing platforms. In trapped ions, progress has largely focused on alkaline-earth and ytterbium ions, whose simple electronic structures facilitate control over their internal state. Here we investigate singly-ionized yttrium ($^{89}\mathrm{Y}^+$), a two-valence-electron ion whose ground-state manifold hosts a nuclear-spin qubit and which also features a variety of low-lying metastable manifolds, for applications in quantum information processing. Because experimental data are limited, we perform high-resolution laser-induced fluorescence spectroscopy to measure the hyperfine structure of several low-lying levels, and carry out comprehensive electronic structure calculations to determine lifetimes, transition matrix elements, and hyperfine coefficients for manifolds addressable with visible, near-visible, or infrared wavelengths. Using these results, we analyze schemes for qubit storage, initialization, readout, leakage mitigation, and single- and two-qubit gates. These results position $^{89}\mathrm{Y}^+$ as a uniquely capable next-generation trapped-ion qubit, combining field-insensitive nuclear-spin or clock-qubit storage with spectrally isolated transitions for operations.