Saturating the quantum Cramér-Rao bound using LOCC

ORAL

Abstract

The quantum Cramér-Rao bound (QCRB) provides an ultimate precision limit allowed by quantum mechanics in parameter estimation. Given any quantum state dependent on a single parameter, there is always a positive-operator valued measurement (POVM) saturating the QCRB. However, the QCRB-saturating POVM cannot always be implemented efficiently, especially in multipartite systems. In this talk, we show that the POVM based on local operations and classical communication (LOCC) is QCRB-saturating for arbitrary pure states or rank-two mixed states with varying probability distributions over fixed eigenbasis. We also analyze the robustness of our LOCC protocol against noise and show how it can be made noise-resilient. Finally, a four-qubit system is studied as an example of a non-trivial LOCC protocol saturating the QCRB. For details, see ArXiv: 1809.06017.

–

Presenters

  • Sisi Zhou

    Department of Physics, Yale University, Yale Quantum Institute, Yale University

Authors

  • Sisi Zhou

    Department of Physics, Yale University, Yale Quantum Institute, Yale University

  • Chang-Ling Zou

    University of Science and Technology of China, Key Laboratory of Quantum Information, University of Science and Technology of China, Yale University, USTC

  • Liang Jiang

    Yale Univ, Department of Physics, Yale University, Yale Quantum Institute, Yale University