Improving the performance of superconducting microwave resonators in magnetic fields

Bothner, Daniel; Gaber, T.; Kemmler, M.; Koelle, D.; Kleiner, R.

doi:10.1063/1.3560480

Cited by 58 publications

(70 citation statements)

References 27 publications

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“…4(b) and 4(d), it is also evident that Q B is power independent 10,19 even down to the single photon regime. This power independence is expected in the high power regime for a narrow zero field cooled strip, 19 and we show that this also holds for extremely low powers.…”

Section: Resultsmentioning

confidence: 89%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic field resilient superconducting fractal resonators for coupling to free spins

Graaf

Danilov

Adamyan

et al. 2012

Journal of Applied Physics

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We demonstrate a planar superconducting microwave resonator intended for use in applications requiring strong magnetic fields and high quality factors. In perpendicular magnetic fields of 20 mT, the niobium resonators maintain a quality factor above 25 000 over a wide range of applied powers, down to single photon population. In parallel field, the same quality factor is observed above 160 mT, the field required for coupling to free spins at a typical operating frequency of 5 GHz. We attribute the increased performance to the current branching in the fractal design. We demonstrate that our device can be used for spectroscopy by measuring the dissipation from a pico-mole of molecular spins. V C 2012 American Institute of Physics. [http://dx

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Section: Resultsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Magnetic field resilient superconducting fractal resonators for coupling to free spins

Graaf

Danilov

Adamyan

et al. 2012

Journal of Applied Physics

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“…Measurements have evaluated the effects of magnetic fields[6] and vortex motion [7]. The remaining dissipation channel is usually attributed to the presence of TLFs.…”

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confidence: 99%

Slow noise processes in superconducting resonators

et al. 2013

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Slow noise processes, with characteristic timescales ∼1s, have been studied in planar superconducting resonators. A frequency locked loop is employed to track deviations of the resonator centre frequency with high precision and bandwidth. Comparative measurements are made in varying microwave drive, temperature and between bare resonators and those with an additional dielectric layer. All resonators are found to exhibit flicker frequency noise which increases with decreasing microwave drive. We also show that an increase in temperature results in a saturation of flicker noise in resonators with an additional dielectric layer, while bare resonators stop exhibiting flicker noise instead showing a random frequency walk process.Slow fluctuations in charge sensitive devices have been frequently examined over the past few decades [1]. Recently, their effects were indirectly observed in superconducting qubits [2] with supporting theoretical work [3] linking them to the presence of two level fluctuators (TLFs) [4]. We present measurements directly probing these slow noise processes in superconducting resonators using a high bandwidth feedback technique with Hz level resolution [5]. Feedback maintains a lock to the resonator centre frequency indefinitely, providing a direct measure of the nature of slow fluctuations and their behavior in varying temperature, microwave drive and TLF density. Theoretical work [3] suggests that 'slow' fluctuators can have a profound -but indirect-effect on the noise and losses in superconducting devices operating at microwave frequencies such as qubits. In simplified terms the model considers two distinct ensembles of TLFs: a coherent population that couples directly to the device, and a 'slow' population which perturbs the coherent TLFs, by changing the tunnel splitting. Hence, whereas the coherent processes between the two energy levels are expected to have short time constants, they are in turn effectively being modulated by processes that can have time constants of the order of seconds or even hours.Motivated by QIP applications, recent studies on superconducting resonators have focused heavily on sources of dissipation. Measurements have evaluated the effects of magnetic fields[6] and vortex motion [7]. 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. However, measuring this noise can be difficult due to the extrinsic low frequency noise present in equipment such as amplifiers and mixers [14]. Here we overcome this problem by using a high-bandwidth measurement metho...

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“…All the Q values quoted throughout this article are loaded quality factors, which approximately equal the internal quality factors of our resonators. 1 The fundamental frequency of the resonators slightly shifts up by increasing W+2S (from ~2.60 GHz for W=20 µm and S=8 µm to ~3.15 GHz for W=60 µm and S=24 µm). This is due to the decrease of effective permittivity (Ԑ eff ) by increasing W+2S [3,4,22,25].…”

Section: Resultsmentioning

confidence: 99%

“…Coplanar waveguides (CPWs) from superconducting [1,2] and metallic (non-superconducting) materials [3][4][5] are widely used in microwave transmission lines. Since conductor strip and ground planes are on the same side of the substrate, they can be easily adapted to active/passive components.…”

Section: Introductionmentioning

confidence: 99%

Metallic coplanar resonators optimized for low-temperature measurements

Rahim¹,

Lehleiter²,

Bothner³

et al. 2016

J. Phys. D: Appl. Phys.

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Metallic coplanar microwave resonators are widely employed at room temperature, but their low-temperature performance has received little attention so far. We characterize compact copper coplanar resonators with multiple modes from 2.5 to 20 GHz at temperatures as low as 5 K. We investigate the influence of center conductor width (20 to 100 µm) and coupling gap size (10 to 50 µm), and we observe a strong increase of quality factor (Q) for wider center conductors, reaching values up to 470. The magnetic-field dependence of the resonators is weak, with a maximum change in Q of 3.5% for an applied field of 7 T. This makes these metallic resonators well suitable for magnetic resonance studies, as we document with electron spin resonance (ESR) measurements at multiple resonance frequencies.

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Improving the performance of superconducting microwave resonators in magnetic fields

Cited by 58 publications

References 27 publications

Magnetic field resilient superconducting fractal resonators for coupling to free spins

Magnetic field resilient superconducting fractal resonators for coupling to free spins

Slow noise processes in superconducting resonators

Metallic coplanar resonators optimized for low-temperature measurements

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