Progress toward development of a strontium atom interferometer for precise gravitational measurements

Abstract

The interplay between quantum mechanics and gravity is almost as mysterious today as it was half a century ago despite remarkable progress in either field. Putting aside exotic topics like quantum theories of gravity, even a purely classical quantity, such as Newton’s gravitational constant (or “big G”), has not been measured to a precision and accuracy close to that of other fundamental constants (e.g. speed of light, fine structure constant, etc.). Moreover, until recently [1], most measurements of big G have been classical in nature. Therefore, using a quantum sensor, such as an atomic gradiometer, to perform precision measurements of big G not only adds another (quantum) dimension to said measurement, but also opens a window into studying other fundamental classical gravitational phenomena, like measuring gravitational waves [2]. Furthermore, due to the quantum nature of the sensor apparatus, the interplay of gravity and quantum mechanics can be explored by studying effects such as gravitational decoherence [3]. In this talk, I will discuss ongoing progress on the construction of a 2 meter tall atom interferometer using Strontium. By virtue of the bosonic isotope (Strontium-88) having a zero nuclear spin, the demands on magnetic shielding of the apparatus are relaxed compared to (say) alkali atoms. Once operational over the 2 meter baseline, this atom interferometer will be used to perform short-distance tests (10 centimeters to 1 meter) of gravity using source (or proof) masses in the 100 kilogram range or higher. The distance between the gravitational sensor (i.e. atom interferometer) and the proof masses can be varied using appropriate translation stages. This measurement configuration will allow us to perform precision measurements of big G. [1] Rosi et al. (2014). Nature 510, 518-521. [2] Abe et al. (2021) Quantum Science and Technology 6, 044003. [3] Roura (2020). Physical Review X 10, 021014.