Many-body Quantum Control of a Spin-1 BEC

Spin-1 condensates provide a useful platform for investigations of atom squeezing,\footnote{C.D. Hamley, \emph{et al.}, Nat. Phys. 8, 305 (2012)} generation of non-Gaussian states,\footnote{C.S. Gerving, \emph{et al.}, Nat. Commun. 3, 1169 (2012)} and dynamical control.\footnote{T.M. Hoang, \emph{et al.}, Phys. Rev. Lett. 111, 090403 (2013)} We demonstrate dynamic control of a quantum many-body spin-1 system that is enabled by strong collisional interactions. In contrast to the usual single-particle quantum control techniques, the method demonstrated here is intrinsically many-body, exploiting the strong collisional interactions. The experiment uses a spin-1 $^{87}$Rb condensate initialized in the $|F=1,m_F=0\rangle$ polar state at a high magnetic field above the quantum phase transition, and then prepared in a coherent state using a rf rotation. The many-body control is implemented by time-varying the relative strength of the Zeeman and spin interaction energies of the condensate at multiples of the natural coherent oscillation frequency of the system. This is a parametric excitation method relying on time varying changes to the Hamiltonian. We will present our experimental results, which compare well to theory, and will discuss future directions and applications.