近日，日本瑞穗研究与技术股份有限公司的Kohei Oshioanonymous与日本庆应义塾大学的Naoki Yamamoto等人合作并取得一项新进展。他们提出了基于变分量子电路的含噪量子振幅估计自适应测量策略。相关研究成果已于2024年12月24日在国际知名学术期刊《物理评论A》上发表。

本文研究了存在未知强度去极化噪声情况下的振幅估计问题。这一问题的主要难点在于，最优测量方式同时依赖于未知的量子状态和要估计的振幅。为了解决这些问题，研究人员利用变分量子电路来近似（未知的）最优测量基，并结合量子估计理论中提出的两步自适应估计策略。数值结果表明，所提方法几乎可以达到量子克拉美-罗下界（QCRB）。

据悉，在量子计算中，振幅估计是各种量子算法中使用的一个基本子程序。这类估计问题的一个重要任务是确定估计的下界，即量子克拉美-罗下界（QCRB），并构造一个能够达到QCRB的最优估计器。

附：英文原文

Title: Adaptive measurement strategy for noisy quantum amplitude estimation with variational quantum circuits

Author: Kohei Oshio, Yohichi Suzuki, Kaito Wada, Keigo Hisanaga, Shumpei Uno, and Naoki Yamamoto

Issue&Volume: 2024-12-24

Abstract: In quantum computation, amplitude estimation is a fundamental subroutine that is utilized in various quantum algorithms. A general important task of such estimation problems is to characterize the estimation lower bound, which is referred to as quantum Cramér-Rao bound (QCRB), and to construct an optimal estimator that achieves QCRB. This paper studies the amplitude estimation in the presence of depolarizing noise with unknown intensity. The main difficulty in this problem is that the optimal measurement depends on both the unknown quantum state and the amplitude we aim to estimate. To deal with these issues, we utilize the variational quantum circuits to approximate the (unknown) optimal measurement basis combined with the two-step adaptive estimation strategy which was proposed in the quantum estimation theory. We numerically show that the proposed method can nearly attain the QCRB.

DOI: 10.1103/PhysRevA.110.062423

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.062423