We store and control ultra-cold atoms in a new type of trap using magnetic fields of vortices in a high temperature superconducting micro-structure. This is the first time ultra-cold atoms have been trapped in the field of magnetic flux quanta. We generate the attractive trapping potential for the atoms by combining the magnetic field of a superconductor in the remanent state with external homogeneous magnetic fields. We show the control of crucial atom trap characteristics such as an efficient intrinsic loading mechanism, spatial positioning of the trapped atoms and the vortex density in the superconductor. The measured trap characteristics are in good agreement with our numerical simulations.Atom-optical systems combined with well-established superconductor technology allows a new generation of fundamental experiments and applications, potentially enabling a coherent interface between neutral atoms and solid-state quantum devices. Important applications include the quantum state transfer and manipulation between atomic and solid-state systems which is of great interest for quantum information. For this goal the combination of atomic or molecular quantum systems with quantum states in superconducting solid-state devices has been proposed in various forms [1,2,3,4,5,6,7,8].Recently, superconducting current-carrying chips have been used to implement micro-traps for neutral atoms [9, 10, 11] and advantages over conventional chips have been shown [12,13,14]. A prominent approach for quantum state manipulation in superconductors utilizes the magnetic flux quantum [15,16,17,18]. The flux quantum is of particular interest as an interface between atomic quantum systems and solid-state quantum devices because atoms with a magnetic dipole moment can be manipulated to high precision using magnetic fields. The pairing of atoms with quantized magnetic flux is a promising way of achieving a controlled interaction with possible applications in quantum technology and fundamental studies. In this article we report the trapping of ultra-cold atoms that relies on the controlled coupling between vortices in a superconductor and the magnetic dipole moment of 87 Rb atoms. This mechanism allows the design of novel trapping or guiding architectures for ultra-cold atoms. Such architectures could be additionally tailored by using combinations of vortices with magnetic fields induced by applied currents in superconducting micro-structures.

We investigate the behavior of electric fields originating from adsorbates deposited on a cryogenic atom chip as it is cooled from room temperature to cryogenic temperature. Using Rydberg electromagnetically induced transparency, we measure the field strength versus distance from a 1 mm square of yttrium barium copper oxide (YBCO) patterned onto a yttria stabilized zirconia chip substrate. We find a localized and stable dipole field at room temperature and attribute it to a saturated layer of chemically adsorbed rubidium atoms on the YBCO. As the chip is cooled towards 83 K we observe a change in sign of the electric field as well as a transition from a localized to a delocalized dipole density. We relate these changes to the onset of physisorption on the chip surface when the van der Waals attraction overcomes the thermal desorption mechanisms. Our findings suggest that through careful selection of substrate materials, it may be possible to reduce the electric fields caused by atomic adsorption on chips, opening up experiments to controlled Rydberg-surface coupling schemes.

We report on the trapping of ultracold atoms in the magnetic field formed entirely by persistent supercurrents induced in a thin film type-II superconducting square. The supercurrents are carried by vortices induced in the 2D structure by applying two magnetic field pulses of varying amplitude perpendicular to its surface. This results in a self-sufficient quadrupole trap that does not require any externally applied fields. We investigate the trapping parameters for different supercurrent distributions. Furthermore, to demonstrate possible applications of these types of supercurrent traps we show how a central quadrupole trap can be split into four traps by the use of a bias field.

We employ the hysteretic behavior of a superconducting thin film in the remanent state to generate different traps and flexible magnetic potentials for ultra-cold atoms. The trap geometry can be programmed by externally applied fields. This new approach for atom-optics is demonstrated by three different trap types realized on a single micro-structure: a Z-type trap, a double trap and a bias field free trap. Our studies show that superconductors in the remanent state provide a new versatile platform for atom-optics and applications in ultra-cold quantum gases.PACS numbers: 37.10.Gh, 03.75.Be, 74.78.NaThe use of superconductors in atom chips [1-3] is a recent development, presenting new opportunities for atom optics [4][5][6][7][8]. One demonstrated advantage of superconductors over conventional conductors is the significant reduction of near-field noise in current-carrying structures leading to low atomic heating rates and enhanced spin-flip lifetimes [9][10][11][12][13][14]. Proposals in this area advocate experimental designs for coherent coupling with atomic or molecular quantum systems that exploit the distinct properties of superconductors [15][16][17][18][19][20][21][22].In a previous paper we have demonstrated that the remanent magnetization created by vortices can be used to trap ultra cold atoms without applying a transport current [23]. Other groups have created quadrupole type traps [24] and have shown that vortices modify the trapping potential created by a transport current in a Z-type trap [25]. In this article, we show that the unique response of superconductors to applied magnetic field enables programmable magnetic trap geometries for ultra cold atoms. We demonstrate this new approach by generating three different atom trap geometries on a fixed superconducting micro-structure. We can choose the geometry by applying a suitable external magnetic field sequence. The trapping potentials are generated by spatial magnetic patterns imprinted on a thin film, using the hysteretic response of type-II superconductors.The three different geometries we realize in this article to demonstrate this new approach are shown schematically in Fig.

We propose and analyze neutral atom traps generated by vortices imprinted by magnetic field pulse sequences in type II superconducting disks and rings. We compute the supercurrent distribution and magnetic field resulting from the vortices in the superconductor. Different patterns of vortices can be written by versatile loading field sequences. We discuss in detail procedures to generate quadrupole traps, self-sufficient traps, and ring traps based on superconducting disks and rings. The ease of creating these traps and the low current noise in supercurrent-carrying structures make our approach attractive for designing atom chip interferometers and probes.