Absolute-phase-shift measurement in a phase-shear-readout atom interferometer

We demonstrate that the shear phase introduced by a tilting Raman beam in a Mach-Zehnder atom interferometer actually shifts the absolute phase, and propose how this shift can be compensated for by reference to a special point of the interference fringe. In the experiment, we obtain shear interference fringes and achieve the extraction of absolute phase corresponding to gravity acceleration. To suppress the impact of position drift on measurement accuracy, we adopt a positive and negative tilt angle alternating measurement (PNTAM) method. After using this PNTAM method, when the position drift leads to a change of 2.2 x 10-3 g, the impact of this drift on the absolute measurement value is less than 1.9 x 10-4 g. This work expands the application range of the phase shear readout based atom interferometer from the current relative or differential gravity measurement to the field of absolute gravity measurement.