High-Fidelity Universal Gate Set for $^9$Be$^+$ Ion Qubits

TL;DR

This paper demonstrates high-fidelity quantum gates on $^9$Be$^+$ ion qubits with very low error rates, achieving long coherence times and paving the way for fault-tolerant quantum computing.

Contribution

It presents a universal gate set with record low error rates on $^9$Be$^+$ ions, including single- and two-qubit gates, with detailed error analysis and reduction strategies.

Findings

Single-qubit gate error of 3.8e-5

Two-qubit gate error of 8e-4 from Bell state fidelity

Memory coherence time exceeds 1 second

Abstract

We report high-fidelity laser-beam-induced quantum logic gates on magnetic-field-insensitive qubits comprised of hyperfine states in $^{9}$Be$^+$ ions with a memory coherence time of more than 1 s. We demonstrate single-qubit gates with error per gate of $3.8(1)\times 10^{-5}$. By creating a Bell state with a deterministic two-qubit gate, we deduce a gate error of $8(4)\times10^{-4}$. We characterize the errors in our implementation and discuss methods to further reduce imperfections towards values that are compatible with fault-tolerant processing at realistic overhead.