Precision measurement with atom interferometry

Development of atom interferometry and its application in precision measurement are reviewed in this paper. The principle, features and the implementation of atom interferometers are introduced, the recent progress of precision measurement with atom interferometry, including determination of gravitational constant and fine structure constant, measurement of gravity, gravity gradient and rotation, test of weak equivalence principle, proposal of gravitational wave detection, and measurement of quadratic Zeeman shift are reviewed in detail. Determination of gravitational redshift, new definition of kilogram, and measurement of weak force with atom interferometry are also briefly introduced.

Calibration of a compact absolute atomic gravimeter

Compact atomic gravimeters are the potential next generation precision instruments for gravity survey from fundamental research to broad field applications.We report the calibration results of our home build compact absolute atomic gravimeter USTC-AG02 at Changping Campus,the National Institute of Metrology(NIM),China in January 2019.The sensitivity of the atomic gravimeter reaches 35.5μGal/√Hz(1μGal=1×10-8 m/s2)and its long-term stability reaches 0.8μGal for averaging over 4000 seconds.Considering the statistical uncertainty,the dominant instrumental systematic errors and environmental effects are evaluated and corrected within a total uncertainty(2σ)of 15.3μGal.After compared with the reference g value given by the corner cube gravimeter NIM-3A,the atomic gravimeter USTC-AG02 reaches the degree of equivalence of 3.7μGal.

Two-frequency amplification in a semiconductor tapered amplifier for cold atom experiments

Simultaneous two-frequency amplification is highly desirable in cold atom experiments. The nonlinear response would appear in the two-frequency amplification with a semiconductor tapered amplifier（TA） and has a direct influence on the experimental result. We investigated in detail the effects of frequency difference, total power, and power ratio of two seeding lasers on the output components based on a simplified theoretical model. The simulation results showed that the multiple sideband generation in the amplifier due to self-phase and amplitude modulation could be suppressed and the TA tended to linearly amplify the power ratio between two-frequency components, when the two seeding lasers had a large frequency difference. This was verified experimentally in the output power ratio measurement via a calibrated Fabry-Perot interferometer method with a good linearity and an uncertainty of 1%. We also discussed the consequences of power ratio responses in the amplification in light of cold atom experiments, especially in the ac Stark shift related phase error of Raman-type atom interferometers（AIs）. It was shown that the fluctuation of intensity ratio of Raman beams may induce significant systematic errors for an AI gyroscope.

Theory of a Kaptiza-Dirac Interferometer with Cold Trapped Atoms

We theoretically analyse a multi-modes atomic interferometer consisting of a sequence of Kapitza-Dirac pulses (KD) applied to cold atoms trapped in a harmonic trap. The pulses spatially split the atomic wave-functions while the harmonic trap coherently recombines all modes by acting as a coherent spatial mirror. The phase shifts accumulated among different KD pulses are estimated by measuring the number of atoms in each output mode or by fitting the density profile. The sensitivity is rigorously calculated by the Fisher information and the Cramér-Rao lower bound. We predict, with typical experimental parameters, a temperature independent sensitivity which, in the case of the measurement of the gravitational constant g can significantly exceed the sensitivity of current atomic interferometers.