Properties of superconducting planar resonators at millikelvin temperatures

Abstract

Planar superconducting resonators are now being increasingly used at mK temperatures in a number of novel applications. They are also interesting devices in their own right since they allow us to probe the properties of both the superconductor and its environment. We have experimentally investigated three types of niobium resonators -including a lumped element design -fabricated on sapphire and SiO2/Si substrates. They all exhibit a non-trivial temperature dependence of their centre frequency and quality factor. Our results shed new light on the interaction between the electromagnetic waves in the resonator and two-level fluctuators in the substrate.

Magnetic field resilient superconducting fractal resonators for coupling to free spins

“…Much attention has been given to studies of coplanar resonators at milliKelvin temperatures in order to pinpoint and eliminate different types of dissipative processes limiting the quality factor. [6][7][8] Several methods have been developed to improve the quality factors in magnetic fields, such as antidots in ground planes and the central conductor of the resonator [9][10][11][12][13] as well as narrow slots in the center conductor 14 to reduce the degrees of freedom for vortices in the superconductor.…”

Minimal resonator loss for circuit quantum electrodynamics

“…Presently used resonators, made from Nb or Al, have quality factors on the order of 10 4 to 10 5 . [2][3][4][5][6] In contrast, superconducting resonators for astronomical photon detection 7 have shown quality factors in excess of a million in the many-photon regime. One would like to maintain these high values down to the single photon level.…”

Slow noise processes in superconducting resonators

“…The remaining dissipation channel is usually attributed to the presence of TLFs. The exact nature of TLFs remains contentious, but a variety of experiments have studied their effects [8][9][10][11][12] and recent models evaluated the contributions of TLFs in varying locations [13].In this letter we study slow noise processes in low loss niobium (Nb) on sapphire resonators [11]. Resonators are by their very nature sensitive probes: any change in the environment will produce a change in the centre frequency ν 0 of the resonator; making them ideal devices for studying noise.…”

“…In this letter we study slow noise processes in low loss niobium (Nb) on sapphire resonators [11]. Resonators are by their very nature sensitive probes: any change in the environment will produce a change in the centre frequency ν 0 of the resonator; making them ideal devices for studying noise.…”

“…The remaining dissipation channel is usually attributed to the presence of TLFs. The exact nature of TLFs remains contentious, but a variety of experiments have studied their effects [8][9][10][11][12] and recent models evaluated the contributions of TLFs in varying locations [13].…”