Microwave response of vortices in superconducting thin films of Re and Al

Song, Cunxian; Heitmann, Tom; DeFeo, M. P.; Yu, K.; McDermott, Robert; Neeley, M.; Martinis, John M.; Plourde, B. L. T.

doi:10.1103/physrevb.79.174512

Cited by 119 publications

(126 citation statements)

References 44 publications

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“…The eventual decrease of T 1 and T 2E at high-magnetic field (B\200 mG) can be attributed to vortices entering the gap capacitors where current density is high. Such dissipation due to vortex flow resistance has been well-known to degrade the quality factor of superconducting resonators and qubits 43,44 . Therefore, precautions such as multilayer magnetic shielding, specialized non-magnetic hardware and honeycombstyle device designs have been widely employed in the community to avoid vortices.…”

Section: Qp Recombination Constant Across Seven Devices (Supplementarymentioning

confidence: 99%

Measurement and control of quasiparticle dynamics in a superconducting qubit

et al. 2014

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Superconducting circuits have attracted growing interest in recent years as a promising candidate for fault-tolerant quantum information processing. Extensive efforts have always been taken to completely shield these circuits from external magnetic fields to protect the integrity of the superconductivity. Here we show vortices can improve the performance of superconducting qubits by reducing the lifetimes of detrimental single-electron-like excitations known as quasiparticles. Using a contactless injection technique with unprecedented dynamic range, we quantitatively distinguish between recombination and trapping mechanisms in controlling the dynamics of residual quasiparticle, and show quantized changes in quasiparticle trapping rate because of individual vortices. These results highlight the prominent role of quasiparticle trapping in future development of superconducting qubits, and provide a powerful characterization tool along the way.

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Section: Qp Recombination Constant Across Seven Devices (Supplementarymentioning

confidence: 99%

Measurement and control of quasiparticle dynamics in a superconducting qubit

et al. 2014

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“…Since Q 0 and Q TLS have similar magnitudes, TLS loss is not dominant even at the lowest power, possibly explaining the absence of a downturn in f 0 versus T , shown in Fig. 2(b).Although a wider gap w g suppresses TLS loss, care must be taken not to introduce loss from trapped vortices, created when the film is cooled through its superconducting transition [17,18]. The effect of the applied field on Q m is shown in Fig.…”

mentioning

confidence: 99%

“…Although a wider gap w g suppresses TLS loss, care must be taken not to introduce loss from trapped vortices, created when the film is cooled through its superconducting transition [17,18]. The effect of the applied field on Q m is shown in Fig.…”

mentioning

confidence: 99%

Improving the coherence time of superconducting coplanar resonators

Wang

Hofheinz

Wenner

et al. 2009

Applied Physics Letters

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162

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The quality factor and energy decay time of superconducting resonators have been measured as a function of material, geometry, and magnetic field. Once the dissipation of trapped magnetic vortices is minimized, we identify surface two-level states (TLS) as an important decay mechanism. A wide gap between the center conductor and the ground plane, as well as use of the superconductor Re instead of Al, are shown to decrease loss. We also demonstrate that classical measurements of resonator quality factor at low excitation power are consistent with single-photon decay time measured using qubit-resonator swap experiments.Superconducting coplanar resonators have many important applications such as photon detection [1] and quantum computation [2,3], and recently have been used to host arbitrary photon states generated by coupling to qubits [4,5,6]. A key parameter limiting the performance is the energy relaxation time T 1 , while dephasing is relatively unimportant [7]. Resonator performance has typically been determined through classical measurements of the quality factor, and much work has yet to be done to understand the physics of the loss mechanisms and to optimize resonator designs for best performance [8,9,10,11,12].Here we show how several previously untested loss mechanisms can be eliminated or optimized to reach a measured quality factor Q m in the 200,000 to 400,000 range at low power, while the intrinsic quality factor Q i is even higher after subtraction of the coupling capacitor limited Q c . We provide detailed evidence that surface loss from two-level state (TLS) defects is an important loss mechanism. Finally, we show how relatively simple quality factor measurements, when taken at low power, can be used to predict the energy decay time of resonators at the single photon level.For this work, we measured various half-wavelength (λ/2) and quarter-wavelength (λ/4) coplanar resonators, as described in Fig. 1 and Table I. Aluminum (Al) films were sputter deposited and etched with a Cl 2 /BCl 3 -based reactive ion etch (RIE), whereas Rhenium (Re) was electron-beam evaporated in a molecular beam epitaxy system using a substrate temperature of 850 • C and etched with SF 6 /O 2 -based RIE. The films were fabricated as part of a multilayer process to enable testing with qubits. Q m of the resonators was determined in an adiabatic demagnetization refrigerator using standard two-port transmission measurements with a vector network analyzer. Q c 's estimated from the |S 21 | calibration were ∼400,000 (∼1,000,000) for λ/2 (λ/4) resonators but were not subtracted from Q m .For all the resonators we observed an increase in Q m as the measurement power increased and temperature T decreased. The T dependence is shown in Fig. 2 power. To avoid complications due to different geometries, we base most of the discussion on λ/4 resonators as they share a similar shape. The decrease in Q m with increasing temperature is consistent with quasiparticle dissipation. In Fig. 2(b), the fractional change in the resonance frequency ∆...

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“…Superconducting stripline (also called triplate) resonators, [35][36][37][38][39] as well as the similar microstrip resonators, [40][41][42][43] have been used since the 1980s to study thin films of superconductors. A related technique are superconducting coplanar resonators, which have also been used to study the microwave properties of superconducting thin films, 44,45 and which recently became very popular for photon detection (as microwave kinetic inductance detectors) 46,47 and in the field of quantum information science (e.g. as building blocks for circuit QED architecture).…”

Section: Introductionmentioning

confidence: 99%

Surface-resistance measurements using superconducting stripline resonators

Hafner

Dressel

Scheffler

2014

Review of Scientific Instruments

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We present a method to measure the absolute surface resistance of conductive samples at a set of GHz frequencies with superconducting lead stripline resonators at temperatures 1 -6 K. The stripline structure can easily be applied for bulk samples and allows direct calculation of the surface resistance without the requirement of additional calibration measurements or sample reference points. We further describe a correction method to reduce experimental background on high-Q resonance modes by exploiting TEM-properties of the external cabling. We then show applications of this method to the reference materials gold, tantalum, and tin, which include the anomalous skin effect and conventional superconductivity. Furthermore, we extract the complex optical conductivity for an all-lead stripline resonator to find a coherence peak and the superconducting gap of lead.

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Microwave response of vortices in superconducting thin films of Re and Al

Cited by 119 publications

References 44 publications

Measurement and control of quasiparticle dynamics in a superconducting qubit

Measurement and control of quasiparticle dynamics in a superconducting qubit

Improving the coherence time of superconducting coplanar resonators

Surface-resistance measurements using superconducting stripline resonators

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