Qubit Reuse Beyond Reorder and Reset: Optimizing Quantum Circuits by Fully Utilizing the Potential of Dynamic Circuits

TL;DR

This paper introduces a novel method for optimizing quantum circuits by fully exploiting dynamic circuit primitives, significantly reducing qubit requirements and outperforming existing approaches on various quantum algorithms.

Contribution

It presents a new approach that moves measurements and uses classically controlled gates to enhance qubit reuse beyond current reordering and reset techniques.

Findings

Reduces qubit count for QPE, QFT, and VQE circuits.

Achieves up to 95% qubit reduction in sparse random circuits.

Outperforms existing qubit reuse methods.

Abstract

Qubit reuse offers a promising way to reduce the hardware demands of quantum circuits, but current approaches are largely restricted to reordering measurements and applying qubit resets. In this work, we present an approach to further optimize quantum circuits by fully utilizing the potential of dynamic quantum circuits-more precisely by moving measurements and introducing dynamic circuit primitives such as classically controlled gates in a way that forges entirely new pathways for qubit reuse. This significantly reduces the number of required qubits for a variety of circuits, creating new opportunities for running complex circuits on near-term devices with limited qubit counts. We show that the proposed approach drastically outperforms existing methods, reducing qubit requirements where previous approaches are unable to do so for popular quantum circuits such as Quantum Phase Estimation (QPE), Quantum Fourier Transform~(QFT), and Variational Quantum Eigensolver (VQE) ans\"atze, as well as leading to improvements of up to 95% for sparse random circuits.