We propose a scalable resonant detector architecture for High-Frequency Gravitational Waves (HFGW) in the GHz band, based on a superconducting microwave bridge interferometer. Thefundamental unit — the Rebellon Bridge — consists of two orthogonal Superconducting Radio Frequency (SRF) cavities fed by a balanced Magic-Tee splitter from a cryogenic sapphire oscillator (CSO). Unlike prior proposals relying on the inverse Gertsenshtein effect (photon-conversion), which scales quadratically with strain (P ∝ h2 ), the Rebellon Bridge exploits parametric modulation of the cavity boundary conditions in the proper detector frame 6 to achieve linear voltage sensitiv-ity (V ∝ h). The Q-factor amplifies phase sensitivity rather than graviton-to-photon conversion efficiency, and the dark-port differential observable provides inherent common-mode rejection of environmental noise. The detection philosophy is grounded in the Rebellon Compensation Principle: just as cosmological redshift is visible only to an observer whose spectral reference lies outside the perturbed metric, the GW signal is readable only at the recombination dark port, where fields fromorthogonally-oriented cavities — each having traversed a different fabric condition — interfere differentially. The single-bridge unit is then extended to a tri-bridge array: three bridge units sharing a single cryogenic enclosure, with three mutually orthogonal CSOs each oriented along the axis least perturbed by its paired bridge plane. This arrangement samples the full three-dimensional GW strain tensor — recovering both polarisations and the propagation direction from a single compact instrument — while the common cryogenic environment ensures that thermal, seismic, electromagnetic, and acoustic noise cancel as common-mode in √ all differential channels simultaneously. A noise budget demonstrates strain sensitivity h ∼ 10−22 / Hz, with detector bandwidth tunable via Q and f0 to cover targets including the primordial stochastic GW background, post-merger neutron stars, ultralight dark matter, and cosmic string networks.
Manuel Rebellón (Fri,) studied this question.