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We describe a matter-wave Sagnac interferometer using Bose condensed atoms confined in a time-orbiting potential trap. Compared to our previous implementation [Moan et al., Phys. Rev. Lett. 124, 120403 (2020)], our new apparatus provides better thermal stability, improved optical access, and reduced trap anharmonicity. The trapping field can be adjusted to compensate for small tilts of the apparatus in gravity. These features enable operation with an effective Sagnac area of 4 mm2 per orbit, and we observe interference with 25% visibility after two orbits at a total interrogation time of 0.6 s. Long-term measurements indicate a phase stability of 0.2 rad or better. [ABSTRACT FROM AUTHOR]

A Sagnac atom interferometer can be constructed using a Bose–Einstein condensate trapped in a cylindrically symmetric harmonic potential. Using the Bragg interaction with a set of laser beams, the atoms can be launched into circular orbits, with two counterpropagating interferometers allowing many sources of common-mode noise to be excluded. In a perfectly symmetric and harmonic potential, the interferometer output would depend only on the rotation rate of the apparatus. However, deviations from the ideal case can lead to spurious phase shifts. These phase shifts have been theoretically analyzed for anharmonic perturbations up to quartic in the confining potential, as well as angular deviations of the laser beams, timing deviations of the laser pulses, and motional excitations of the initial condensate. Analytical and numerical results show the leading effects of the perturbations to be second order. The scaling of the phase shifts with the number of orbits and the trap axial frequency ratio are determined. The results indicate that sensitive parameters should be controlled at the 10 − 5 level to accommodate a rotation sensing accuracy of 10 − 9 rad/s. The leading-order perturbations are suppressed in the case of perfect cylindrical symmetry, even in the presence of anharmonicity and other errors. An experimental measurement of one of the perturbation terms is presented. [ABSTRACT FROM AUTHOR]