Certified Fidelity Susceptibility from Classical Shadows

Fidelity susceptibility is a useful probe of quantum phase transitions and quantum metrology, but its direct evaluation on a quantum device is challenging. By integrating Krylov-subspace methods with a resolvent-based reformulation, we present a method for certifying fidelity susceptibility using randomized single-copy measurements across repeated ground-state preparations. The resulting approximations form monotone lower bounds to the exact fidelity susceptibility and converge geometrically. We also present applications to metrology and linear static susceptibilities.

Source: arXiv:2608.24732v1 - http://arxiv.org/abs/2608.24732v1 PDF: https://arxiv.org/pdf/2608.24732v1 Original Link: http://arxiv.org/abs/2608.24732v1