Phase-modulated entangling gates robust to static and time-varying errors

TL;DR

This paper introduces a phase-modulated entangling gate scheme for trapped ion qubits that significantly enhances robustness against static and dynamic errors, achieving high fidelity and scalability benefits.

Contribution

The authors experimentally demonstrate a phase modulation technique that minimizes residual excitation errors in entangling gates, improving robustness and scalability in quantum systems.

Findings

Achieved 99.4% average gate fidelity in trapped ion qubits.

Reduced gate errors under common experimental error sources.

Verified robustness improvements through system-identification experiments.

Abstract

Entangling operations are among the most important primitive gates employed in quantum computing and it is crucial to ensure high-fidelity implementations as systems are scaled up. We experimentally realize and characterize a simple scheme to minimize errors in entangling operations related to the residual excitation of mediating bosonic oscillator modes that both improves gate robustness and provides scaling benefits in larger systems. The technique employs discrete phase shifts in the control field driving the gate operation, determined either analytically or numerically, to ensure all modes are de-excited at arbitrary user-defined times. We demonstrate an average gate fidelity of 99.4(2)% across a wide range of parameters in a system of $^{171}\text{Yb}^{+}$ trapped ion qubits, and observe a reduction of gate error in the presence of common experimental error sources. Our approach provides a unified framework to achieve robustness against both static and time-varying laser amplitude and frequency detuning errors. We verify these capabilities through system-identification experiments revealing improvements in error-susceptibility achieved in phase-modulated gates.