Sagnac-based rotation sensing with superfluid helium quantum interference devices

The Sagnac effect has played an instrumental role for the fundamental studies of relativity, and various devices that utilize this effect have been applied to many disciplines ranging from inertial navigation to geodesy and to seismology. In this context we present an overview of recent developments related to superfluid helium quantum interference devices. With the discovery of superfluid Josephson phenomena in He 4 , the device technology has been rapidly developing in the past 10 years. We discuss the underlying working principles of these interference devices and their applications. We focus on their use as sensitive rotation sensors based on the Sagnac effect coupled with the existence of a macroscopic quantum phase via particle–wave duality.