Dual atomic interferometry for differential inertial sensing

Abstract

The utilization of light-pulse atom interferometry presents a valuable technique that has found application in both fundamental scientific inquiries, such as investigating constants such as measurements of fine structure constant α and gravitational constant G, and practical endeavors including acceleration sensing and rotation measurements. This thesis delves into our implementation of a dual atom interferometer design involving the clock transition 1S0 → 3P0 in strontium, concurrently conducting the interferometric sequence on atoms in both ground and excited states.

To facilitate the dual atom interferometer’s operation, we have firstly established a compact experimental setup with a transversely loaded bi-dimensional magneto-optical-trap (2D-MOT) to create a high flux source of cold strontium atoms. Introducing a novel cross-polarized bi-color atomic beam slower, we simultaneously addresses two excited Zeeman substates of the transition 1S0 → 1P1 in strontium-88, significantly enhancing the number of atoms prepared in the 461 nm MOT by around 10-fold. Following the 461 nm MOT, the atomic ensemble undergoes cooling in a 689 nm MOT, achieving atomic temperatures below 1 µK. We also install a network of eight magnetic field probes arranged around the cold atomic sample, enabling precise three-axis active control of magnetic fields down to the milligauss level.

With the atoms confined in a 2D lattice at the magic-wavelength of 813.427 nm after the initial preparation phase, we conduct the magnetically-induced clock transition to create a statistical mixture state of ground and excited states. After a velocity selection stage, implementing a Mach-Zehnder interferometer with Bragg pulses operating at the magic-wavelength along the vertical axis, we conduct tests of the weak equivalence principle (WEP).

The Eötvös ratio we found in our system stood at (1.8 ± 3.1) × 10−4, mainly limited by the finite temperature of the atomic cloud constraining the interrogation time. Furthermore, the dual atom interferometer scheme enables the measurement of state-dependent force and eventually polarizability difference via the phase shift between the atoms in different states, and we experimentally demonstrate this by introducing an additional light field gradient.