Time-domain nonlinear quantum interferometry
Phys. Rev. A 113, 023706 – Published 10 February, 2026
DOI: https://doi.org/10.1103/f252-64sy
Abstract
Interferometry is a powerful method for studying many fundamental phenomena ranging from gravitational waves to anyon excitations. Aside from loss of coherence in the interferometer paths, quantum mechanics sets an incompressible bound for linear interferometry arising from the quantum noise of the light beam, called the shot-noise limit. Here, we implement a nonlinear quantum interferometer that uses a microwave cavity and a magnetic field resilient anharmonic superconducting quantum circuit made of granular aluminum. The circuit enables interferometry beyond the shot-noise limit. A direct application of our findings is the detection of dark matter (axions or dark photons), high-frequency gravitational waves, or astronomical masers.
