  Geometric phase is a key player in many areas of quantum science and
technology. In this review article, several foundational aspects of quantum
geometric phases and their relations to classical geometric phases are
outlined. How the Aharonov--Bohm and Sagnac effects fit into this context is
then discussed. Moreover, a concise overview of technological applications of
the latter, with special emphasis on gravitational sensing, like in gyroscopes
and gravitational wave detectors is presented.
