Fast, high-fidelity addressed single-qubit gates using efficient composite pulse sequences

TL;DR

This paper demonstrates high-speed, high-fidelity single-qubit gates on $^{43} ext{Ca}^{+}$ ions using microwave control and composite pulse sequences, with errors below 2×10⁻⁵, scalable to multiple qubits.

Contribution

It introduces an efficient composite pulse scheme for addressed single-qubit gates with record fidelity and speed in a cryogenic ion trap system.

Findings

Single-qubit error rate of 1.5×10⁻⁶ per Clifford gate.

Two-qubit addressed gates with error rate 3.4×10⁻⁵ per π/2-gate.

Scheme is scalable to larger qubit registers.

Abstract

We use electronic microwave control methods to implement addressed single-qubit gates with high speed and fidelity, for $^{43}\text{Ca}^{+}$ hyperfine "atomic clock" qubits in a cryogenic (100K) surface trap. For a single qubit, we benchmark an error of $1.5$ $\times$ $10^{-6}$ per Clifford gate (implemented using $600~\text{ns}$ $\pi/2$-pulses). For two qubits in the same trap zone (ion separation $5~\mu\text{m}$), we use a spatial microwave field gradient, combined with an efficient 4-pulse scheme, to implement independent addressed gates. Parallel randomized benchmarking on both qubits yields an average error $3.4$ $\times$ $10^{-5}$ per addressed $\pi/2$-gate. The scheme scales theoretically to larger numbers of qubits in a single register.