Efficient Quantum Control via Automatic Control Skips

TL;DR

This paper introduces a general method for identifying skippable parts in quantum circuits to reduce gate count and depth, providing a practical approach despite the NP-hardness of the problem.

Contribution

It presents a generic, polynomial-time approximation algorithm for finding skippable subcircuits in quantum operations, improving circuit efficiency.

Findings

Over 50% improvement in circuit metrics on real-world applications

Proves NP-hardness of optimal skippable pattern identification

Provides a practical approximation approach for quantum control optimization

Abstract

Control of quantum operations is a crucial yet expensive construct for quantum computation. Efficient implementations of controlled operations often avoid applying control to certain subcircuits, which can significantly reduce the number of gates and overall circuit depth. However, these methods are specialized and circuits frequently need to be implemented manually. This paper presents a generic method for finding "skippable" patterns without having to tailor implementations for each algorithm. We prove that finding the optimal operations to be skipped is generally NP-hard. Nevertheless, sub-optimal, polynomial approximation algorithms that find skippable subcircuits can lead to over $50\%$ improvement in circuit metrics for real-world applications.