We characterize the performance of a gravimeter and a gravity gradiometer based on the 1 S 0 -3 P 0 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 , 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 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 achieve 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 88 Sr 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., 87 Sr, Ca, Yb).

An innovative and practical scheme of building laser power stabilization system is proposed by using external-control method. A high-speed Field Programmable Gate Array (FPGA) is used as real-time controller, which makes the closed-loop control period of only 4.175μs and response time for stabilizing process less than 90μs. The typical noises affecting the laser power is analyzed. Experimental results show that the system has a high stability improvement with stability of output laser keeps around 2‰ whether the input laser is free running or frequency scanning, which proves the competent performance to satisfy high request of laser power stability in cold atom experiments. What’s more, the laser power stabilization system can be embedded as a functional module into the FPGA based timing sequence system in cold atom interferometry, which makes the laser power be controllable accurately by the way of time sequence.

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