title: Controlling the hyperfine state of rovibronic ground-state polar molecules.
abstract: We report the preparation of a rovibronic ground-state molecular quantum gas in a single hyperfine state and, in particular, the absolute lowest quantum state. This addresses the last internal degree of freedom remaining after the recent production of a near quantum degenerate gas of molecules in their rovibronic ground state, and provides a crucial step towards full control over molecular quantum gases. We demonstrate a scheme that is general for bialkali polar molecules and allows the preparation of molecules in a single hyperfine state or in an arbitrary coherent superposition of hyperfine states. The scheme relies on electric-dipole, two-photon microwave transitions through rotationally excited states and makes use of electric nuclear quadrupole interactions to transfer molecular population between different hyperfine states.
authors.affiliation: JILA, National Institute of Standards and Technology and University of Colorado, and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, USA.
authors.forename: S
authors.initials: S
authors.lastname: Ospelkaus
authors.forename: K-K
authors.initials: KK
authors.lastname: Ni
authors.forename: G
authors.initials: G
authors.lastname: Quéméner
authors.forename: B
authors.initials: B
authors.lastname: Neyenhuis
authors.forename: D
authors.initials: D
authors.lastname: Wang
authors.forename: M H G
authors.initials: MH
authors.lastname: de Miranda
authors.forename: J L
authors.initials: JL
authors.lastname: Bohn
authors.forename: J
authors.initials: J
authors.lastname: Ye
authors.forename: D S
authors.initials: DS
authors.lastname: Jin