Improving and benchmarking NISQ qubit routers

TL;DR

This paper benchmarks various qubit routing techniques for NISQ devices, introducing a new fidelity metric and demonstrating significant improvements with SABRE-based methods, emphasizing the importance of hardware-specific routing choices.

Contribution

It introduces a comprehensive circuit fidelity metric and applies a SABRE-based approach to significantly improve qubit routing performance on NISQ devices.

Findings

Up to 84% higher average circuit fidelity with SABRE-based routing.

Routing performance depends on qubit count and hardware characteristics.

Benchmarking on 1D and 2D lattice connectivities shows variable effectiveness.

Abstract

Quantum computers with a limited qubit connectivity require inserting SWAP gates for qubit routing, which increases gate execution errors and the impact of environmental noise due to an overhead in circuit depth. In this work, we benchmark various routing techniques considering random quantum circuits on one-dimensional and square lattice connectivities, employing both analytical and numerical methods. We introduce circuit fidelity as a comprehensive metric that captures the effects of SWAP and circuit depth overheads. Leveraging a novel approach based on the SABRE algorithm, we achieve up to $84\%$ higher average circuit fidelity for large devices within the NISQ range, compared to previously existing methods. Additionally, our results highlight that the optimal routing choice critically depends on the qubit count and the hardware characteristics, including gate fidelities and coherence times.