Optically tailored trapping geometries for ultracold atoms on a type-II superconducting chip

Abstract

Superconducting atom chips have very significant advantages in realizing trapping structures for ultracold atoms compared to conventional atom chips. We extend these advantages further by developing the ability to dynamically tailor the superconducting trap architecture. Heating the chosen parts of a superconducting film by transferring optical images onto its surface we are able to modify the current density distribution and create desired trapping potentials. This method enables us to change the shape and structure of magnetic traps, enabling versatile applications in atomtronics.In the past years, superconducting (SC) atom chips have drawn a lot of attention for trapping and manipulating ultracold atoms 1-9 . Due to the suppression of magnetic field noise close to superconducting surfaces, SC atom chips are excellent candidates for quantum information applications 10-17 . Moreover they will enable the realization of hybrid quantum systems composed of ultracold atoms and superconducting circuits, thereby merging the advantages of these two technologies 18-30 .Owing to the characteristic properties of superconductors, magnetic traps for the confinement of neutral atoms on a SC atom chip can be created by either transport currents 31-33 , persistent currents 34-36 , or trapped magnetic fields induced by pinned vortices 37-39 . For transport and persistent currents the trap type is determined by the shape of the current carrying wire and therefore cannot be changed during experiments. Magnetic traps generated by vortices inside type-II superconductors allow a more flexible approach. Depending on the history of the applied magnetic fields and transport currents, various traps with or without external bias fields can be created by the same superconducting structures. In addition, such traps are easier to manipulate using external magnetic fields. These traps are, however, limited to simple geometries and do not allow one to change the distribution of vortices locally 40-42 .In this paper we describe in detail how to configure the vortex distribution in a square SC film in order to create the desired potential without the need of changing the chip or the applied field. We make use of a high-power laser and a DMD (digital micromirror device) to destroy the superconductivity in selected regions of the film and influence the shape and structure of a trap. We have been able to realize various trapping potentials and, in particular, to split a single trap or to transform it into a crescent or a ring-like trap. Since the atomic cloud FIG. 1. Schematic diagram of the setup. A Gaussian beam of a high power laser is patterned with a DMD and imaged onto a superconducting chip attached to a cryostat inside vacuum. The vortex distribution is probed by absorption imaging 43 of the atoms after illumination.evolves with the trapping potential, cold atoms can be used as a sensitive probe to examine the real-time magnetic field and vortex distribution. We experimentally verified the possibility of controlling trap geometry by local l...

A scanning quantum cryogenic atom microscope at 6 K

“…However, combining atomic cooling and trapping techniques with the cryogenic cooling of nearby materials is technically challenging. Such systems have been built for the purpose of, e.g., trapping atoms with superconducting wires and/or near superconducting materials [6][7][8][9][10][11][12][13][14][15], increasing the lifetime of trapped ions [16,17], and creating hybrid quantum information devices by coupling atoms to superconducting qubits [18]. Scanning probe sensing with a BEC or ultracold thermal gas has been previously demonstrated [5,[19][20][21][22]; however, no other apparatus but the SQCRAMscope serves as a scanning probe for quantum materials with the capability of rapid sample exchange and BEC recovery, high-numerical-aperture imaging, and wide-area sample imaging [1,2].…”

Advances in Atomtronics

“…As optical techniques have improved, it has become possible to produce not only honeycomb [ 3 ] and Kagomé lattices [ 4 ], but custom optical lattices using holographic masks [ 5 ]. Customized potential well structures for ultracold atoms can also be generated using atom chips [ 6 ], acoustic optical modulators (AOMs) [ 7 ], and digital micromirror devices (DMDs) [ 8 ].…”

Advances in atomtronics

“…As optical techniques have improved it has become possible to produce, not only honeycomb [3] and Kagomé lattices [4], but custom optical lattices using holographic masks [5]. Customized potential well structures for ultracold atoms can also be generated using atom chips [6], accoustic optical modulators [AOMs] [7] and digital micromirror devices [DMDs] [8].…”