Experiments with laser cooling and cold spinor gases

Abstract

This thesis is the result of work on two separate Bose-Einstein condensate (BEC) experiments. First, I describe several projects in the construction of an ultracold Er and Na mixture experiment (Er:Na experiment). These include the design and characterization of a high temperature induction oven for Er as well as the capture of Er atoms into a 2D magneto-optical trap (2D MOT). Together, the induction oven and 2D MOT constitute a novel, compact source of cold Er atoms. Additionally, the construction and characterization of high current magnetic field coils for a magnetic quadrupole trap (MQT) and Helmholtz coils for future Feshbach spectroscopy are detailed.Second, I describe a series of experiments with spinor gases carried out on the JQI Na spinor apparatus. In the first experiment, I demonstrate the freezing of nonlinear spin mixing dynamics in a 23Na BEC using a microwave dressing. This technique can be used to preserve squeezing of a probe state in future metrological applications. The spinor phase of a frozen state evolves at an enhanced rate proportional an effective quadratic Zeeman shift, q, of the |F = 1, mF = 0⟩ energy level. In the second experiment, I demonstrate a radio frequency (rf) atomic spin-1 Ramsey interferometer which can measure the effective q, and thereby the spinor phase precession rate of a frozen probe state. The interferometer can simultaneously measure the rf detuning and q, and I demonstrate that it can be operated in both resonant and off-resonant regimes, using differential phase modulation between the two Ramsey pulses. The spin-1 Ramsey interferometer therefore has distinct advan- tages over both rf and microwave Rabi spectroscopy which are alternative methods to measure the effective q. Finally, I demonstrate theoretical grounds for spin squeezing in a cold spin-1 thermal gas. In particular, I derive a spin-1 Boltzmann transport equation for the Wigner phase space density operator without recourse to Hartree-Fock theory. I then apply three different theoretical paradigms to model an experimental observation of classical relative number squeezing in a cold spin-1 thermal gas of Na: a simplified undepleted pump model which I solved analytically, a semiclassical quasiprobability distribution (QPD) numerical method, and numerical solution of the Schro ̈dinger equation using Fock states.