Programmable trap geometries with superconducting atom chips

Abstract

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.

Inhomogeneous dark states of atomic-molecular Bose-Einstein condensates in trapping potentials

“…We constructed such potentials with various depths and widths. We notice that realization of the required geometries of the potentials is experimentally feasible nowadays, since even much more sophisticated configurations have already been implemented in laboratories (see, e.g., [11], where a rapidly moving laser beam creating time-averaged dipole traps was implemented, or [12] where traps programmable by an external field were created using superconducting thin films). Next we have studied the stability of the trapped atomic-molecular states.…”

“…This reflects a simple fact that deeper potentials allow for trapping more atoms and molecules. From (12), one also observes that the case of positive scattering lengths (i.e., repulsive interactions) requires deeper potentials to keep the particles together, compared to the case of attractive interactions.…”

Design of magnetic traps for neutral atoms with vortices in type-II superconducting microstructures

“…In previous experimental investigations [26], we measured the location of the vortex-based magnetic atom trap to be stable over ∼ 2 hours. This confirms that any thermal relaxation of the vortices does not affect the overall macroscopic magnetization of the superconductor on the experiment timescale.…”

Heating rate and spin flip lifetime due to near-field noise in layered superconducting atom chips

“…The reduction of the spin flip rate has been shown experimentally for different chip types: with and without a gold layer above the superconductor [10][11][12][13]. The purpose of the top gold layer in atom chips is to use them in mirror-MOTs [26].…”

“…In the area of magnetic trapping of ultracold atoms, considerable attention has been recently devoted to the interaction of atomic clouds with the surfaces of both superconducting atom chips [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and superconducting solid state devices [17][18][19][20]. Technological advances will allow a new generation of fundamental experiments and applications involving the control of the interface between atomic systems and quantum solid state devices.…”