Tight trade-off relation and optimal measurement for multiparameter quantum estimation
Phys. Rev. A 114, 012609 – Published 8 July, 2026
DOI: https://doi.org/10.1103/m1z7-f7b8
Abstract
In multiparameter quantum estimation, the optimal measurements for different parameters encoded in a quantum state are in general incompatible, giving rise to nontrivial tradeoffs between their attainable levels of precision. Understanding and characterizing such tradeoffs is essential for determining the ultimate precision limits in multiparameter quantum estimation, and it is therefore a central topic in quantum metrology. In this article, we present an approach that precisely quantifies the tradeoff resulting from incompatible optimal measurements in multiparameter estimation. We derive a tight analytical tradeoff relation that determines the ultimate precision limits for estimating an arbitrary number of parameters encoded in pure quantum states. Additionally, we provide a systematic methodology for constructing optimal measurements that saturate this tight bound in an analytical and structured manner. To demonstrate the power of our findings, we apply our methodology to quantum radar, resulting in a refined Arthurs-Kelly relation that characterizes the ultimate performance for the simultaneous estimation of range and velocity.
