Error-Resilient Fast Entangling Gates for Scalable Ion-Trap Quantum Processors

TL;DR

This paper presents an improved, error-resilient method for implementing fast two-qubit entangling gates in large ion-trap quantum processors, achieving high fidelity and robustness against noise.

Contribution

It introduces a multi-objective machine design approach for scalable, error-resilient fast entangling gates in ion-trap systems, allowing arbitrary ion pair operations with high fidelity.

Findings

Achieves microsecond two-qubit gates with ~99.9% fidelity in 50-ion chains.

Eliminates laser phase noise susceptibility through symmetry-imposed pulse sequences.

Demonstrates robustness against random and systematic experimental errors.

Abstract

Non-adiabatic two-qubit gate proposals for trapped-ion systems offer superior performance and flexibility over adiabatic schemes at the cost of increased laser control requirements. Existing fast gate schemes are limited by single-qubit transition errors, which constrain the total number of pulses in high-fidelity solutions. We introduce an improved gate search scheme that enables both local and non-local two-qubit gates in chains containing tens of ions. These protocols use a multi-objective machine design approach that incorporates dominant sources of error in the design to ensure the solutions are compatible with existing fast laser controls. We also generalize previous schemes by allowing for unpaired pulses during the gate evolution. By imposing symmetries on the pulse sequences, we eliminate susceptibility to laser phase noise and further simplify the multi-mode control over the state-dependent motion of the ion crystal. We perform a comprehensive analysis of expected gate performance in the presence of random and systematic experimental errors to demonstrate the feasibility of performing microsecond two-qubit gates between arbitrary ion pairs in current linear ion-trap processors of up to $50$ ions with fidelities approaching $99.9\%$.