title: Interferometry with non-classical motional states of a Bose-Einstein condensate.
abstract: The Ramsey interferometer is a prime example of precise control at the quantum level. It is usually implemented using internal states of atoms, molecules or ions, for which powerful manipulation procedures are now available. Whether it is possible to control external degrees of freedom of more complex, interacting many-body systems at this level remained an open question. Here we demonstrate a two-pulse Ramsey-type interferometer for non-classical motional states of a Bose-Einstein condensate in an anharmonic trap. The control sequences used to manipulate the condensate wavefunction are obtained from optimal control theory and are directly optimized to maximize the interferometric contrast. They permit a fast manipulation of the atomic ensemble compared to the intrinsic decay processes and many-body dephasing effects. This allows us to reach an interferometric contrast of 92% in the experimental implementation.
authors.affiliation: Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Stadionallee 2, A-1020 Vienna, Austria.
authors.forename: S
authors.initials: S
authors.lastname: van Frank
authors.affiliation: 1] Zentrum für Optische Quantentechnologien, Universität Hamburg, The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, D-22761 Hamburg, Germany [2] Institut für Quanteninformationsverarbeitung, Universität Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Negretti
authors.affiliation: Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Stadionallee 2, A-1020 Vienna, Austria.
authors.forename: T
authors.initials: T
authors.lastname: Berrada
authors.affiliation: 1] Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Stadionallee 2, A-1020 Vienna, Austria [2] Max Planck Institute for the Structure and Dynamics of Matter, Bldg. 99 (CFEL), Luruper Chaussee 149, D-22761 Hamburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Bücker
authors.affiliation: 1] Institut für Quanteninformationsverarbeitung, Universität Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany [2] Center for Integrated Quantum Science and Technology (IQST), Universität of Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Montangero
authors.affiliation: Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Stadionallee 2, A-1020 Vienna, Austria.
authors.forename: J-F
authors.initials: JF
authors.lastname: Schaff
authors.affiliation: Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Stadionallee 2, A-1020 Vienna, Austria.
authors.forename: T
authors.initials: T
authors.lastname: Schumm
authors.affiliation: 1] Institut für Quanteninformationsverarbeitung, Universität Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany [2] Center for Integrated Quantum Science and Technology (IQST), Universität of Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Calarco
authors.affiliation: Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Stadionallee 2, A-1020 Vienna, Austria.
authors.forename: J
authors.initials: J
authors.lastname: Schmiedmayer