title: Optimal control of complex atomic quantum systems.
abstract: Quantum technologies will ultimately require manipulating many-body quantum systems with high precision. Cold atom experiments represent a stepping stone in that direction: a high degree of control has been achieved on systems of increasing complexity. However, this control is still sub-optimal. In many scenarios, achieving a fast transformation is crucial to fight against decoherence and imperfection effects. Optimal control theory is believed to be the ideal candidate to bridge the gap between early stage proof-of-principle demonstrations and experimental protocols suitable for practical applications. Indeed, it can engineer protocols at the quantum speed limit - the fastest achievable timescale of the transformation. Here, we demonstrate such potential by computing theoretically and verifying experimentally the optimal transformations in two very different interacting systems: the coherent manipulation of motional states of an atomic Bose-Einstein condensate and the crossing of a quantum phase transition in small systems of cold atoms in optical lattices. We also show that such processes are robust with respect to perturbations, including temperature and atom number fluctuations.
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: Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Stadionallee 2, A-1020 Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Bonneau
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
authors.affiliation: Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Hild
authors.affiliation: Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Gross
authors.affiliation: Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany.|Laboratoire Charles Fabry, Institut d'Optique - CNRS - Université Paris Saclay, 91127 Palaiseau, France.
authors.forename: M
authors.initials: M
authors.lastname: Cheneau
authors.affiliation: Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Bloch
authors.affiliation: Institute for complex quantum systems &Center for Integrated Quantum Science and Technology (IQST), Universität Ulm, Albert-Einstein-Allee 11, D-89075 Ulm, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Pichler
authors.affiliation: Zentrum für Optische Quantentechnologien and The Hamburg Centre for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, D-22761 Hamburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Negretti
authors.affiliation: Institute for complex quantum systems &Center for Integrated Quantum Science and Technology (IQST), Universität Ulm, Albert-Einstein-Allee 11, D-89075 Ulm, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Calarco
authors.affiliation: Institute for complex quantum systems &Center for Integrated Quantum Science and Technology (IQST), Universität Ulm, Albert-Einstein-Allee 11, D-89075 Ulm, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Montangero