Inductively coupled superconducting half wavelength resonators as persistent current traps for ultracold atoms

Abstract

A crucial point in the experimental implementation of hybrid quantum systems consisting of superconducting circuits and atomic ensembles is bringing the two partners close enough to each other that a strong quantum coherent coupling can be established. Here, we propose to use the metallization structures of a half wavelength superconducting coplanar waveguide resonator as a persistent current trap for ultracold paramagnetic atoms. Trapping atoms with the resonator structure itself is provided by using short-ended and inductively coupled resonators instead of capacitively coupled ones as customary in circuit quantum electrodynamics. We analyze the external quality factor of short-ended coplanar waveguide resonators and show that it can be easily designed for the desired regime of quantum circuits. The magnetic field configuration at the resonator is calculated by means of numerical three-dimensional simulations of the London equations. We present a way to transport an atomic ensemble into the coplanar resonator gap where the magnetic field of the cavity mode is maximum. The configuration allows stable trapping by persistent currents and paves the route toward strong coupling between atomic clouds and the cavity mode which is required for cooperative effects and gives the interface between atoms and circuit quantum electrodynamics.

Quantum technologies with hybrid systems

“…Nevertheless, magnetic trapping and even cooling of a cloud of atoms down to quantum degeneracy [i.e., to Bose-Einstein condensation (BEC)] above a superconducting chip has been demonstrated (71,72). New ways of using superconducting resonators and circuits directly for trapping are currently being explored (73). Other experimental approaches to the realization of atomic HQSs are being pursued (74), where atoms are optically trapped in the evanescent field of a tapered fiber (75).…”

Dynamics of a dipolar Bose-Einstein condensate in the vicinity of a superconductor

“…So far we have only discussed small amplitude oscillations and have seen that the resulting frequency shift can be described very accurately using approximation (23). In Fig.…”

“…This allows lifetimes several orders of magnitudes longer than in conventional microtraps [10][11][12][13]. Such superconducting microtraps allow studying fundamental interactions between BECs and superconductors and promise coupling of these two macroscopic quantum phenomena [14][15][16][17][18][19][20][21][22][23].…”

Current-induced magnetization hysteresis defines atom trapping in a superconducting atomchip

“…They provide advantages like reduced Johnson-Nyquist noise [9,25,28] compared to normal conducting wires [29] and the possibility to create a noise-free trap without any external connection to provide a transport current [6,21,23,26]. Bringing ultracold atoms close to superconducting resonators allows to create hybrid quantum systems [17,30,31], coupling superconducting quantum electronics [32] to atomic quantum memory. They can also form a platform to study Rydberg atoms [10,33,34] and create novel superconducting trap arrays for quantum simulation [35,36].…”