Matter-wave analog of a fiber-optic gyroscope
Katarzyna Krzyżanowska, Jorge Ferreras, Changhyun Ryu, E. Carlo Samson, M. G. Boshier
Abstract
Confining the propagating wave packets of an atom interferometer inside a waveguide can substantially reduce the size of the device while preserving high sensitivity. We have realized a two-dimensional Sagnac atom interferometer in which Bose-condensed $^{87}\mathrm{Rb}$ atoms propagate within a tight waveguide formed by a collimated laser beam, a matter wave analog of the fiber optic gyro. The condensate is split, reflected, and recombined with a series of Bragg pulses while the waveguide moves transversely so that the wave-packet trajectories enclose an area. Delta-kick cooling is used to prepare low-density atomic wave packets with a temperature of $3\phantom{\rule{0.16em}{0ex}}\mathrm{n}\mathrm{K}$. The low density reduces the impact of interatomic interactions, while the low temperature limits the expansion of the wave packet during the interferometer cycle. The effective enclosed area is $0.8\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\mathrm{m}{\mathrm{m}}^{2}\phantom{\rule{0.16em}{0ex}}$ with an average fringe contrast of 20% and underlying contrast up to 60%. The main source of the reduced average contrast is phase noise caused by mechanical vibrations of the optical components. We present a measurement of Allan deviation for such an atom rotation sensor, showing that the interferometer phase noise falls with averaging time $\ensuremath{\tau}$ as ${\ensuremath{\tau}}^{\ensuremath{-}1/2}$ for $\ensuremath{\tau}$ up to 10 000 seconds. The statistical noise falls below the Earth rotation rate after 30 minutes of averaging.