Sr atom interferometry with the optical clock transition as a gravimeter and a gravity gradiometer

We characterize the performance of a gravimeter and a gravity gradiometer based on the 1S0-3P0 clock transition of strontium atoms. We use this new quantum sensor to measure the gravitational acceleration with a relative sensitivity of 1.7 × 10-5 after 150 s of integration time, representing the first realisation of an atomic interferometry gravimeter based on a single-photon transition. Various noise contributions to the gravimeter are measured and characterized, with the current primary limitation to sensitivity seen to be the intrinsic noise of the interferometry laser itself. In a gravity gradiometer configuration, a differential phase sensitivity of 1.53 rad (√Hz)-1 was achieved at an artificially introduced differential phase of π/2 rad. We experimentally investigated the effects of the contrast and visibility based on various parameters and achieved a total interferometry time of 30 ms, which is longer than previously reported for such interferometers. The characterization and determined limitations of the present apparatus employing 88Sr atoms provides a guidance for the future development of large-scale clock-transition gravimeters and gravity gradiometers with alkali-earth and alkali-earth-like atoms (e.g. 87Sr, Ca, Yb, Cd).