| dc.description.abstract | The primary purpose of this thesis is to study the generation of quantum entanglement via nonlinear processes in hot sodium vapors and ultracold sodium spinor Bose-Einstein condensates. The creation of entanglement can induce quantum squeezing. Such squeezing has important applications for metrology with quantum-enhanced precision beyond the classical limit, known as quantum-enhanced sensing. In this thesis, I present my research on generating quantum entangled states of light in hot atomic vapors via four-wave mixing and generating quantum entangled atoms in ultracold spinor Bose-Einstein condensates via spin-mixing dynamics.
Non-degenerate four-wave mixing (4WM) in a hot atomic vapor cell has been shown to be an effective method to produce quantum entangled states of light. Most of the recent work on entangled states of light has focused on Rb and Cs in the near infrared regime. Generating entangled light near the Na resonance at 589 nm is challenging but beneficial for interfacing with cold gases and atomic sensors based on Na. I present our investigation on 4WM in a double-Lambda configuration on the Doppler-broadened D1 line of Na. The construction and characterization of a 4WM apparatus to generate entangled light via hot sodium vapor is introduced. The calculation of susceptibilities in the presence of the light fields and 4WM gain is presented. Experimentally, we characterized the 4WM gain and noise properties of the intensity difference between the generated beams of light. In addition, I discuss directions to boost 4WM gain and reduce absorption loss, including a new design of a stainless steel vapor cell and application of saturated absorption light. The squeezed states of light generated by 4WM can be used to enhance the signal-to-noise ratio of atom number measurements of our sodium spinor Bose-Einstein condensates, where entangled states of atoms can be created via spin-mixing.
A Bose-Einstein condensate (BEC) is a novel state of matter where identical bosonic particles occupy the same quantum state below an ultracold critical temperature. I present our experimental system for an all-optical production of sodium spinor BECs. We verify that the matter wave coherence of the BEC, where particles share the same quantum wave function and phase, can be extended to the internal spin degrees of freedom in a spin-1 BEC by observing coherent spin-exchange collisions. Spin-exchange collisions in F=1 spinor BECs, where two atoms with magnetic quantum number m_F=0 collide and change into a pair with m_F=+/-1, are useful to implement matter-wave quantum optics in spin space, such as quantum-enhanced interferometry, because the collisions generate entanglement and they can be precisely controlled using microwave dressing. We demonstrate control of the coherent spin evolution by controlling initial states and using microwave dressing fields during the evolution process to apply quenches. Using these control methods, we experimentally investigate atomic interferometry based on spin-exchange collisions in the regime of long evolution times where the Bogoliubov and truncated Wigner approximations break down, and compare the results with our numerical simulations. The results of our atomic interferometry experiments are promising and suggest a pathway to achieve quantum-enhanced sensitivities and/or enhanced sensitivities given the nonlinear nature of our measurements. | en_US |
