一句话：提出编译器辅助的量子比特复用方法，借助中途测量动态电路减少量子资源占用并提升保真度。
过去量子测量只能安排在电路末尾，否则会引入显著错误，因此已测量的量子比特无法在后续计算中复用。随着 IBM 等硬件开始原生支持中途测量的动态电路，这一限制被打破。本文提出编译器辅助工具 CaQR，自动寻找并利用量子比特复用、保真度、门数与电路时长之间的权衡：识别哪些已完成测量的量子比特可被安全复用，并判断给定应用是否值得复用。作者在真实硬件上以 Bernstein-Vazirani 等代表性应用进行评估，实验表明电路资源占用可降低最多 80%，保真度可提升最多 20%；其中 Bernstein-Vazirani 实机实验资源降低 60%、保真度提升 15%。
Quantum measurement is important to quantum computing as it extracts out the outcome of the circuit at the end of the computation. Previously, all measurements have to be done at the end of the circuit. Otherwise, it will incur significant errors. But it is not the case now. Recently IBM starts supporting dynamic circuit through hardware (instead of software by simulator). With mid-circuit hardware measurement, we can improve circuit efficacy and fidelity from three aspects: (a) reduced qubit usage, (b) reduced swap insertion, and (c) improved fidelity. We demonstrate this using real-world applications Bernstein Verizani on real hardware and show that circuit resource usage can be improved by 60%, and circuit fidelity can be improved by 15%. We design a compiler-assisted tool that can find and exploit the tradeoff between qubit reuse, fidelity, gate count, and circuit duration. We also developed a method for identifying whether qubit reuse will be beneficial for a given application. We evaluated our method on a representative set of important applications. We can reduce resource usage by up to 80% and improve circuit fidelity by up to 20%.
@inproceedings{paperbot10104,
title = {CaQR: A Compiler-Assisted Approach for Qubit Reuse through Dynamic Circuit},
author = {Fei Hua and Yuwei Jin and Yanhao Chen and Suhas Vittal and Kevin Krsulich and Lev S. Bishop and John Lapeyre and Ali Javadi-Abhari and Eddy Z. Zhang},
booktitle = {ASPLOS},
year = {2023},
doi = {10.1145/3582016.3582030}
}