Optimised fast gates for quantum computing with trapped ions

TL;DR

This paper introduces an optimized two-phase method for designing fast, high-fidelity entangling gates in trapped ion quantum computers, outperforming previous schemes especially at sub-microsecond timescales.

Contribution

It presents a novel two-phase optimization approach and two new gate schemes that significantly improve speed and fidelity in trapped ion systems.

Findings

Achieved orders of magnitude higher fidelities for sub-microsecond gates.

Demonstrated superior performance of new schemes over existing methods.

Analyzed the impact of pulse imperfections on gate fidelity.

Abstract

We present an efficient approach to optimising pulse sequences for implementing fast entangling two-qubit gates on trapped ion quantum information processors. We employ a two-phase procedure for optimising gate fidelity, which we demonstrate for multi-ion systems in linear Paul trap and microtrap architectures. The first phase involves a global optimisation over a computationally inexpensive cost function constructed under strong approximations of the gate dynamics. The second phase involves local optimisations that utilise a more precise ODE description of the gate dynamics, which captures the non-linearity of the Coulomb interaction and the effects of finite laser repetition rate. We propose two novel gate schemes that are compatible with this approach, and we demonstrate that they outperform existing schemes in terms of achievable gate speed and fidelity for feasible laser repetition rates. In optimising sub-microsecond gates in microtrap architectures, the proposed schemes achieve orders of magnitude higher fidelities than previous proposals. Finally, we investigate the impact of pulse imperfections on gate fidelity and evaluate error bounds for a range of gate speeds.