title: Sensitivity of ultracold atoms to quantized flux in a superconducting ring.
abstract: We report on the magnetic trapping of an ultracold ensemble of (87)Rb atoms close to a superconducting ring prepared in different states of quantized magnetic flux. The niobium ring of 10  μm radius is prepared in a flux state n Φ(0), where Φ(0)=h/2e is the flux quantum and n varying between ±6. An atomic cloud of 250 nK temperature is positioned with a harmonic magnetic trapping potential at ∼18  μm distance below the ring. The inhomogeneous magnetic field of the supercurrent in the ring contributes to the magnetic trapping potential of the cloud. The induced deformation of the magnetic trap impacts the shape of the cloud, the number of trapped atoms, as well as the center-of-mass oscillation frequency of Bose-Einstein condensates. When the field applied during cooldown of the chip is varied, the change of these properties shows discrete steps that quantitatively match flux quantization.
authors.affiliation: CQ Center for Collective Quantum Phenomena and their Applications in LISA+, Physikalisches Institut, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Weiss
authors.affiliation: CQ Center for Collective Quantum Phenomena and their Applications in LISA+, Physikalisches Institut, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Knufinke
authors.affiliation: CQ Center for Collective Quantum Phenomena and their Applications in LISA+, Physikalisches Institut, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Bernon
authors.affiliation: CQ Center for Collective Quantum Phenomena and their Applications in LISA+, Physikalisches Institut, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Bothner
authors.affiliation: CQ Center for Collective Quantum Phenomena and their Applications in LISA+, Physikalisches Institut, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Sárkány
authors.affiliation: CQ Center for Collective Quantum Phenomena and their Applications in LISA+, Physikalisches Institut, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Zimmermann
authors.affiliation: CQ Center for Collective Quantum Phenomena and their Applications in LISA+, Physikalisches Institut, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Kleiner
authors.affiliation: CQ Center for Collective Quantum Phenomena and their Applications in LISA+, Physikalisches Institut, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Koelle
authors.affiliation: CQ Center for Collective Quantum Phenomena and their Applications in LISA+, Physikalisches Institut, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Fortágh
authors.affiliation: CQ Center for Collective Quantum Phenomena and their Applications in LISA+, Physikalisches Institut, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Hattermann