Common-mode noise rejection using fringe-locking method in WEP test by simultaneous dual-species atom interferometers

We theoretically investigate the application of the fringe-locking method(FLM) in the dual-species quantum test of the weak equivalence principle(WEP).With the FLM,the measurement is performed invariably at the midfringe,and the extraction of the phase shift for atom interferometers is linearized.For the simultaneous interferometers,this linearization enables a good common-mode rejection of vibration noise,which is usually the main limit for high precision WEP tests of the dual-species kind.We note that this method also allows for an unbiased determination of the gravity accelerations difference,which meanwhile is ready to be implemented.     

Measurement of Density Inhomogeneity for Source Masses in Time-of-Swing Method of Measuring G

A method with scanning electron microscopy （SEM） is presented to measure the density inhomogeneity of the stainless steel （SS316） sphere prepared for measuring G using time-of-swing method. The experimental result shows that the relative density inhomogeneity of the sphere is better than 5.9 × 10^-4 over the volume of 0.272 ×0.234× 0.005 mm^3. If we assume that the density inhomogeneity of the spheres used in our G measurement is the same as that of the sphere destroyed in testing, it will contribute to G value with an uncertainty of less than 0.034 ppm in our G measurement. Furthermore, the mass centre offset from the geometric centre of the sphere will be less than 4.3× 10^-4 μm due to this inhomogeneity.