Matter wave interferometers have the potential to reveal some of the most fascinating phenomena of the quantum world. I will discuss research to probe new physics with superfluid ⁴He quantum interference devices.

After a brief introduction on superfluid ⁴He Josephson junctions, I will describe how we configure our interference devices to explore aspects of fundamental physics that have remained elusive in the past. I will highlight some recent interferometry results including (1) the demonstration of superfluid ⁴He gyroscopes, (2) a direct verification of the link between two successful models of superfluidity: the Landau two fluid approach and the Onsager-Feynman-Anderson wavefunction description, (3) the detection of motion of a single vortex line, (4) the linearization of a ⁴He interferometer, and (5) the development of a superfluid quantum interference grating.