Superconducting Levitated Detector of Gravitational Waves

A magnetically levitated mass couples to gravity and can act as an effective gravitational wave detector. We show that a superconducting sphere levitated in a quadrupolar magnetic field, when excited by a gravitational wave, will produce magnetic field fluctuations that can be read out using a flux tunable microwave resonator. With a readout operating at the standard quantum limit, such a system could achieve broadband strain noise sensitivity of $h\lesssim {10}^{-20}\mathrm{/}\sqrt{\mathrm{H}\mathrm{z}}$ for frequencies of $1\mathrm{k}\mathrm{H}\mathrm{z}-1\mathrm{M}\mathrm{H}\mathrm{z}$, opening new corridors for astrophysical probes of new physics.