Low noise magnetic fields in ultracold experiment

Ferrari, Gabriele, Rogora, Chiara

Jacob Scott

The first generation Ultracold Strontium Optical Lattice Clock has achieved an uncertainty on the order of 10^-18 using a 1D optical lattice. The next generation clock is now being constructed with the goal of achieving uncertainties on the 10^-19 level. To achieve this goal, the system will be upgraded to a 3D optical lattice and new apparatus is being built with lower noise and better compatibility with this new system. This thesis discusses the design and construction of the current driving system for the magnetic fields in the experiment. It also presents the design, construction, and testing of the magnetic fields of the Magneto-Optical Trap. Lastly, it analyzes the noise of the generated magnetic fields in the experiment to confirm they commit to the low noise goal of the next generation experiment.

Gediminas Juzeliūnas, Julius Ruseckas, Patrik Öhberg

A. Farolfi, Dimitrios Trypogeorgos, G. Colzi +3 more

We report on the design, construction, and performance of a compact magnetic shield that facilitates a controlled, low-noise environment for experiments with ultracold atomic gases. The shield was designed to passively attenuate external slowly varying magnetic fields while allowing for ample optical access. The geometry, number of layers, and choice of materials were optimized using extensive finite-element numerical simulations. The measured performance of the shield is in good agreement with the simulations. From measurements of the spin coherence of an ultracold atomic ensemble, we demonstrate a residual field noise of 2.6 μG and a suppression of external dc magnetic fields by more than five orders of magnitude.

Xiao-Tian Xu, Zong-Yao Wang, Rui-Heng Jiao +3 more

A ultralow noise magnetic field is essential for many branches of scientific research. Examples include experiments conducted on ultracold atoms, quantum simulations, and precision measurements. In ultracold atom experiments specifically, a bias magnetic field will often serve as a quantization axis and be applied for Zeeman splitting. As atomic states are usually sensitive to magnetic fields, a magnetic field characterized by ultralow noise as well as high stability is typically required for experimentation. For this study, a bias magnetic field is successfully stabilized at 14.5 G, with the root mean square value of the noise reduced to 18.5 μG (1.28 ppm) by placing μ-metal magnetic shields together with a dynamical feedback circuit. Long-time instability is also regulated consistently below 7 μG. The level of noise exhibited in the bias magnetic field is further confirmed by evaluating the coherence time of a Bose-Einstein condensate characterized by Rabi oscillation. It is concluded that this approach can be applied to other physical systems as well.

Kevin A. Twedt, Xianli Zhang, S. L. Rolston