%0 Journal Article %J Physical Review Letters %D 2009 %T Quantum Phase Transitions and Continuous Observation of Spinor Dynamics in an Antiferromagnetic Condensate %A Yingmei Liu %A Sebastian Jung %A Stephen E. Maxwell %A Lincoln D. Turner %A Eite Tiesinga %A Paul. D. Lett %X Condensates of spin-1 sodium display rich spin dynamics due to the antiferromagnetic nature of the interactions in this system. We use Faraday rotation spectroscopy to make a continuous and minimally destructive measurement of the dynamics over multiple spin oscillations on a single evolving condensate. This method provides a sharp signature to locate a magnetically tuned separatrix in phase space which depends on the net magnetization. We also observe a phase transition from a two- to a three-component condensate at a low but finite temperature using a Stern-Gerlach imaging technique. This transition should be preserved as a zero-temperature quantum phase transition. %B Physical Review Letters %V 102 %8 2009/3/23 %G eng %U http://arxiv.org/abs/0902.3189v1 %N 12 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.102.125301