  Gyroscopes play a crucial role in many and diverse applications associated
with navigation, positioning, and inertial sensing [1]. In general, most
optical gyroscopes rely on the Sagnac effect -- a relativistically induced
phase shift that scales linearly with the rotational velocity [2,3]. In ring
laser gyroscopes (RLGs), this shift manifests itself as a resonance splitting
in the emission spectrum that can be detected as a beat frequency [4]. The need
for ever-more precise RLGs has fueled research activities towards devising new
approaches aimed to boost the sensitivity beyond what is dictated by
geometrical constraints. In this respect, attempts have been made in the past
to use either dispersive or nonlinear effects [5-8]. Here, we experimentally
demonstrate an altogether new route based on non-Hermitian singularities or
exceptional points in order to enhance the Sagnac scale factor [9-13]. Our
results not only can pave the way towards a new generation of ultrasensitive
and compact ring laser gyroscopes, but they may also provide practical
approaches for developing other classes of integrated sensors.
