Locality-aware Qubit Routing for the Grid Architecture

TL;DR

This paper introduces a locality-aware qubit routing algorithm tailored for grid architectures, optimizing circuit depth and speed, crucial for NISQ-era quantum computing with limited qubit coherence times.

Contribution

The paper presents a novel graph-theoretic routing algorithm for grid architectures that outperforms existing methods in speed and circuit depth.

Findings

Comparable circuit depth to existing algorithms, better on random permutations

Significantly faster than approximate token swapping implementations

Effective for NISQ-era quantum circuit optimization

Abstract

Due to the short decohorence time of qubits available in the NISQ-era, it is essential to pack (minimize the size and or the depth of) a logical quantum circuit as efficiently as possible given a sparsely coupled physical architecture. In this work we introduce a locality-aware qubit routing algorithm based on a graph theoretic framework. Our algorithm is designed for the grid and certain "grid-like" architectures. We experimentally show the competitiveness of algorithm by comparing it against the approximate token swapping algorithm, which is used as a primitive in many state-of-the-art quantum transpilers. Our algorithm produces circuits of comparable depth (better on random permutations) while being an order of magnitude faster than a typical implementation of the approximate token swapping algorithm.