Experimental Realization of Josephson Junctions for an Atom SQUID

Abstract

We report the creation of a pair of Josephson junctions on a toroidal dilute gas Bose-Einstein condensate (BEC), a configuration that is the cold atom analog of the well-known dc superconducting quantum interference device (SQUID). We observe Josephson effects, measure the critical current of the junctions, and find dynamic behavior that is in good agreement with the simple Josephson equations for a tunnel junction with the ideal sinusoidal current-phase relation expected for the parameters of the experiment. The junctions and toroidal trap are created with the painted potential, a time-averaged optical dipole potential technique which will allow scaling to more complex BEC circuit geometries than the single atom-SQUID case reported here. Since rotation plays the same role in the atom SQUID as magnetic field does in the dc SQUID magnetometer, the device has potential as a compact rotation sensor.

Rapid cooling to quantum degeneracy in dynamically shaped atom traps

“…While an additional CPM degree of freedom from a second orthogonal AOM can allow more control over atom cloud compression [27] or final BEC shape [28,29], it is unlikely that it will provide significant improvements to the speed and efficiency of evaporative cooling that we have demonstrated here. In our current implementation, we choose the vertical waist and large initial CPM amplitude to load about 50% of the compressed MOT.…”

Conical refraction: fundamentals and applications

“…A range of applications of this technique can be envisioned: for optimized beam geometries, i.e., small w 0 , R 0 , and z R , the toroidal dark focus of the PDR generated by CR could be used to built an all-optical trap for BECs using a single beam. Under such conditions, this potential could be used as a basic element in atomic SQUID experiments [216,217], as well as to study the dynamics of matter waves with periodic boundary conditions and the generation of persistent currents [208,218]. For large R 0 , the PDR can be used as a dark 2D ring potential by using a 1D light sheet, along the axial direction, as an additional confining potential.…”

Correlated Dynamics in a Synthetic Lattice of Momentum States

“…While such interaction-driven phenomena are well studied in the two-mode case [34][35][36][37][38][39][40], MSLs offer unique capabilities for engineering multiply-connected lattice geometries [41]. In particular, we consider the effects that local, attractive interactions can have on particle dynamics in MSLs with closed tunneling pathways, where artificial magnetic fluxes play a nontrivial role [10,42].…”

“…2, we explore atom dynamics on lattices with triangular and rhomboidal geometries, attainable in one physical dimension with a combination of first-and second-order Bragg transitions (nearest-and next-nearest-neighbor tunnelings, respectively) [42]. We first consider the simplest such configuration, consisting of three sites with periodic boundary conditions, which is an analog of multiply-connected superconducting quantum interference devices or atomtronic circuits [41]. Figure 2(a) illustrates triple-well dynamics in the pres-ence of a very weak applied flux (0.001π) and uniform tunneling amplitude t. Without interactions (upper plot), an initially localized wavepacket spreads almost evenly to the neighboring sites.…”