Wang, J (reprint author), Chinese Acad Sci, Wuhan Inst Phys & Math, State Key Lab Magnet Resonance & Atom & Mol Phys, Wuhan Natl Lab Optoelect, Wuhan 430071, Peoples R China.
We report an improved test of the weak equivalence principle by using a simultaneous Rb-85-Rb-87 dual-species atom interferometer. We propose and implement a four-wave double-diffraction Raman transition scheme for the interferometer, and demonstrate its ability in suppressing common-mode phase noise of Raman lasers after their frequencies and intensity ratios are optimized. The statistical uncertainty of the experimental data for Eotvos parameter. is 0.8 x 10(-8) at 3200 s. With various systematic errors corrected, the final value is eta = (2.8 +/- 3.0) x 10(-8). The major uncertainty is attributed to the Coriolis effect.