We introduce the 'smooth gate', an entangling method for trapped-ion qubits where residual spin-motion entanglement errors are adiabatically eliminated by ramping the gate detuning. We demonstrate electronically controlled two-qubit gates with an estimated error of 8.4(7)×10−5 without ground-state cooling. We further show that the error remains ≲5×10−4 for ions with average phonon occupation up to nˉ=9.4(3) on the gate mode. These results indicate that trapped-ion quantum computation can achieve high fidelity at temperatures above the Doppler limit, which enables faster and simpler device operation.
@article{arxiv.2510.17286,
title = {Trapped-ion two-qubit gates with >99.99% fidelity without ground-state cooling},
author = {A. C. Hughes and R. Srinivas and C. M. Löschnauer and H. M. Knaack and R. Matt and C. J. Ballance and M. Malinowski and T. P. Harty and R. T. Sutherland},
journal= {arXiv preprint arXiv:2510.17286},
year = {2025}
}