We report on the progress toward a dual-species cadmium and strontium atom interferometer for fundamental physics tests. We have developed and characterized a complete baseline laser system for cadmium, which provides the high power and narrow linewidth necessary for laser cooling and trapping and for performing atom interferometry, with upgraded systems for strontium also implemented. An overview of a design for cooling cadmium is presented, and we outline the basic design of a Cd–Sr atomic fountain, discussing atom launching techniques and the possible role of blackbody radiation. The excellent properties of cadmium and strontium, both individually and as a test pair, are discussed along with the enabled fundamental physics program of tests of the weak equivalence principle and the measurement of relativistic time dilation effects in quantum superpositions of clocks.
We report on the progress toward a dual-species cadmium and strontium atom interferometer for fundamental physics tests. We have developed and characterized a complete baseline laser system for cadmium, which provides the high power and narrow linewidth necessary for laser cooling and trapping and for performing atom interferometry, with upgraded systems for strontium also implemented. An overview of a design for cooling cadmium is presented, and we outline the basic design of a Cd–Sr atomic fountain, discussing atom launching techniques and the possible role of blackbody radiation. The excellent properties of cadmium and strontium, both individually and as a test pair, are discussed along with the enabled fundamental physics program of tests of the weak equivalence principle and the measurement of relativistic time dilation effects in quantum superpositions of clocks.
Matter-wave interferometers operating as clocks and gravimeters allow for precision measurements of time and gravity at unprecedented levels. In all these sensors, the exquisite control of both the internal (electronic) and external (center-of-mass motion) degrees of freedom of ultracold atomic samples enable interactions at their most basic, quantum level to be studied, paving the way for new tests of fundamental physics. For all these applications, novel interferometric schemes based on the narrow intercombination transitions of alkali-earth (and alkali-earth like) atoms have recently gained considerable attention. Here we present the work towards the realization of a simultaneous atom interferometer with cadmium and strontium atoms and the potential physics such a system could explore, along the idea of the ERC - “TICTOCGRAV” EU research project. In particular, we present the design and implementation of the high-power UV laser sources necessary for performing atom interferometry with cadmium and the prospects for developing a high-flux, cold source of cadmium. Potential applications of a simultaneous cadmium and strontium atom interferometer, including to weak equivalence principle and quantum time dilation tests, are discussed.
Atom interferometers with their extremely high sensitivity to inertial forces are an excellent method for investigating and understanding gravity and its gradients. Studying gravity using quantum mechanical test sources, such as ultra-cold atoms, is an exciting choice for probing physics at this intersection. Here work is presented towards the realization of novel atom interferometers based upon Cd and Sr atoms, which posses a common electronic structure with two valence electrons, also providing access to narrow linewidth intercombination transitions. For these experiments, a novel, high-power, tunable, narrow-linewidth VECSEL source has been developed, which acts as a master source to produce continuous light at either 461 nm or 229 nm, corresponding to the cooling transitions in Sr and Cd atoms, respectively. The laser systems for accessing the clock transition and also the inter-combination transition have also been implemented. The current design of the vacuuum chamber is presented, which involves the transfer of the prepared ultracold atomic clouds from preparatory chambers to a science chamber. Towards this, we have also simulated the generation of a cold atomic source of Cd, which is a key component in producing a high sensitivity atom interferometer.
Atom interferometry is a maturing quantum technology which provides one of the most precise approaches to explore fundamental physics, e.g. to search for dark matter, and one day to observe gravitational waves in the frequency range from 10 mHz - 10 Hz. Standard atom interferometers use Bragg or Raman two-photon transitions for the coherent manipulation of matter waves. In a Michelson configuration for atom-aided gravitational waves detection, two orthogonal arms are built to reject laser noise, in the same way as optical interferometers. Atom interferometers utilizing an optical clock transition for coherent manipulation are less affected by the technical noise of the laser, and as a result that single baseline detectors become feasible.At LP2N, we are building a vertical gravity-gradiometer based on atom interferometry using strontium atoms probed on such a clock transition. The final experimental setup will implement a 6-meter tall atomic fountain to realize gradiometry with two or more separated atomic clouds.In my dissertation, I present the realization of the experimental setup in all its sub-systems, and the first experiments with atoms at millikelvin temperature obtained with the first cooling stage with blue light. The laser system for the second red cooling phase and for the coherent manipulation is ready; meanwhile, we realized a dual-frequency Zeeman slower that improves the atomic flux by a factor of six. We also present a study of an original scheme to achieve pulsed and fast light-atom interaction in a narrow-linewidth cavity by exploiting the Stark shift as a high bandwidth switch; this technique could open to the use of narrow-linewidth cavities – and notably their high power buildup - in several contexts, like atom interferometry and quantum information.
The use of strontium in an atom interferometer presents the opportunity to perform detailed measurements of gravitational fields, rotation rates, and clock transitions as well as other natural phenomena. Strontium can be particularly effective in atom interferometry experiments for two reasons. The first is that the intrinsic magnetic properties of strontium result in less sensitivity of the transition frequencies to magnetic noise, allowing for better measurements. Second, strontium atoms can be cooled to a lower temperature just through ordinary Doppler cooling than other atoms typically used in interferometry (e.g., rubidium). A lower temperature means less initial kinetic energy and hence lower spatial dispersion over the course of an experiment. A magneto-optical trap consisting of two primary cooling lasers and two repump lasers cools and confines strontium atoms for use in the interferometer. This thesis focuses on the repump lasers and includes the design and performance of the optical system that frequency stabilizes each laser. The system demonstrated the ability to simultaneously frequency lock the two repump lasers to the degree necessary to form a strontium magneto-optical trap.
Abstract We present a novel optimised design for a source of cold atomic cadmium, compatible with continuous operation and potentially quantum degenerate gas production. The design is based on spatially segmenting the first and second-stages of cooling with the strong dipole-allowed 1S0-1P1 transition at 229 nm and the 326 nm 1S0-3P1 intercombination transition, respectively. Cooling at 229 nm operates on an effusive atomic beam and takes the form of a compact Zeeman slower (∼5 cm) and two-dimensional magneto-optical trap (MOT), both based on permanent magnets. This design allows for reduced interaction time with the photoionising 229 nm photons and produces a slow beam of atoms that can be directly loaded into a three-dimensional MOT using the intercombination transition. The efficiency of the above process is estimated across a broad range of experimentally feasible parameters via use of a Monte Carlo simulation, with loading rates up to 108 atoms s−1 into the 326 nm MOT possible with the oven at only 100 ∘C. The prospects for further cooling in a far-off-resonance optical-dipole trap and atomic launching in a moving optical lattice are also analysed, especially with reference to the deployment in a proposed dual-species cadmium-strontium atom interferometer.
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.