title: Parametric excitation and squeezing in a many-body spinor condensate.
abstract: Atomic spins are usually manipulated using radio frequency or microwave fields to excite Rabi oscillations between different spin states. These are single-particle quantum control techniques that perform ideally with individual particles or non-interacting ensembles. In many-body systems, inter-particle interactions are unavoidable; however, interactions can be used to realize new control schemes unique to interacting systems. Here we demonstrate a many-body control scheme to coherently excite and control the quantum spin states of an atomic Bose gas that realizes parametric excitation of many-body collective spin states by time varying the relative strength of the Zeeman and spin-dependent collisional interaction energies at multiples of the natural frequency of the system. Although parametric excitation of a classical system is ineffective from the ground state, we show that in our experiment, parametric excitation from the quantum ground state leads to the generation of quantum squeezed states.
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
authors.forename: T M
authors.initials: TM
authors.lastname: Hoang
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
authors.forename: M
authors.initials: M
authors.lastname: Anquez
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Robbins
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
authors.forename: X Y
authors.initials: XY
authors.lastname: Yang
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Land
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Hamley
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Chapman