Simple broadband signal detection at the fundamental limit

Broadband detection of a weak oscillatory field with unknown carrier frequency underlies magnetometry, axion searches and gravitational-wave sensing. We show that the Grover-like integration-time lower bound for this task is a geometric corollary an upper bound on the integrated quantum Fisher information, a metrological constraint. We further give an all-analog multi-resonant protocol based on a randomized Su-Schrieffer-Heeger control Hamiltonian and an m-register GHZ probe and verify near-optimal scaling through simulation.

💡 Research Summary

This paper addresses the fundamental time‑complexity limit for detecting a weak oscillatory (AC) field whose carrier frequency is unknown and may lie anywhere within a broad spectral band. The authors first formalize the detection task as a promise problem AC