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    Direct measurement of the quantum geometric tensor in pseudo-Hermitian systems

    Ze-Hao Huang1,2,*, Hai-Tao Ding3,4,†, and Li-Jun Lang5,6,‡

    • 1National Laboratory of Solid State Microstructures and School of Physics, Nanjing University, Nanjing 210093, China
    • 2Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
    • 3Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
    • 4MajuLab, CNRS-UNS-NUS-NTU International Joint Research Unit, Singapore UMI 3654, Singapore
    • 5Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou 510006, China
    • 6Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou 510006, China

    • *Contact author: zhhuang98@smail.nju.edu.cn
    • †Contact author: htding.9@nus.edu.sg
    • ‡Contact author: ljlang@scnu.edu.cn

    Phys. Rev. A 112, 062225 – Published 18 December, 2025

    DOI: https://doi.org/10.1103/x8tj-bhwz

    Abstract

    The quantum geometric tensor (QGT) fundamentally encodes the geometry and topology of quantum states in both Hermitian and non-Hermitian regimes. While adiabatic perturbation theory links its real part (quantum metric) and imaginary part (Berry curvature) to energy fluctuations and generalized forces, respectively, in Hermitian systems, direct measurement of the QGT, which is defined using both left and right eigenstates of a non-Hermitian Hamiltonian, remains challenging. Here we develop two quantum simulation schemes to directly extract all components of the QGT in pseudo-Hermitian systems with real spectra. Each scheme independently determines the complete QGT using generalized expectation values of either the energy fluctuation operator or the generalized force operator with respect to two time-evolved states prepared through distinct nonadiabatic evolutions, thereby establishing two self-contained measurement protocols. We illustrate the validity of these schemes on two q-deformed two-band models: one with nontrivial topology and the other with a nonvanishing off-diagonal quantum metric. Numerical simulations demonstrate that, for suitably chosen nonadiabatic ramp velocities, both schemes achieve high-fidelity agreement with theoretical predictions for measuring the QGT in both models and successfully capture the topological phase transition of the first model using Chern numbers calculated from Berry curvatures. For larger velocities, the generalized force scheme yields greater accuracy for the real part of the QGT, while the energy fluctuation scheme better captures its imaginary part. This work establishes a framework for extending dynamical measurement schemes from Hermitian to pseudo-Hermitian systems with real spectra.

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