High-fidelity two-qubit quantum logic gates using trapped calcium-43 ions

TL;DR

This paper demonstrates high-fidelity two-qubit quantum gates in trapped calcium-43 ions, achieving the fastest and lowest-error gates to date, with detailed analysis of error sources affecting fidelity.

Contribution

It reports the implementation of two-qubit gates with unprecedented speed and fidelity in trapped calcium-43 ions, along with comprehensive error characterization.

Findings

Gate fidelities up to 99.9% achieved

Gate times as short as 3.8 microseconds

Error sources identified and quantified

Abstract

We study the speed/fidelity trade-off for a two-qubit phase gate implemented in $^{43}$Ca$^+$ hyperfine trapped-ion qubits. We characterize various error sources contributing to the measured fidelity, allowing us to account for errors due to single-qubit state preparation, rotation and measurement (each at the $\sim0.1\%$ level), and to identify the leading sources of error in the two-qubit entangling operation. We achieve gate fidelities ranging between $97.1(2)\%$ (for a gate time $t_g=3.8\mu$s) and $99.9(1)\%$ (for $t_g=100\mu$s), representing respectively the fastest and lowest-error two-qubit gates reported between trapped-ion qubits by nearly an order of magnitude in each case.