Crosstalk Suppression for Fault-tolerant Quantum Error Correction with Trapped Ions

TL;DR

This paper investigates crosstalk errors in trapped-ion quantum computers, models their effects, and proposes strategies to suppress them, aiming to improve fault-tolerant quantum error correction performance.

Contribution

It provides a microscopic model of crosstalk errors, compares coherent and incoherent error models, and discusses active suppression strategies at the gate level.

Findings

Crosstalk significantly impacts fault-tolerant QEC performance.

Active suppression strategies can mitigate crosstalk effects.

Identifies experimental targets for achieving beneficial QEC in trapped ions.

Abstract

Physical qubits in experimental quantum information processors are inevitably exposed to different sources of noise and imperfections, which lead to errors that typically accumulate hindering our ability to perform long computations reliably. Progress towards scalable and robust quantum computation relies on exploiting quantum error correction (QEC) to actively battle these undesired effects. In this work, we present a comprehensive study of crosstalk errors in a quantum-computing architecture based on a single string of ions confined by a radio-frequency trap, and manipulated by individually-addressed laser beams. This type of errors affects spectator qubits that, ideally, should remain unaltered during the application of single- and two-qubit quantum gates addressed at a different set of active qubits. We microscopically model crosstalk errors from first principles and present a detailed study showing the importance of using a coherent vs incoherent error modelling and, moreover, discuss strategies to actively suppress this crosstalk at the gate level. Finally, we study the impact of residual crosstalk errors on the performance of fault-tolerant QEC numerically, identifying the experimental target values that need to be achieved in near-term trapped-ion experiments to reach the break-even point for beneficial QEC with low-distance topological codes.