High-frequency flux noise from quasiparticles
ORAL
Abstract
The presence of flux noise in superconducting circuits hinders the coherence and scalability of qubits based on superconducting technology. Experiments show that flux noise follows the empirical power law 1/ωα in the lower frequency range ħω « kBT, with exponent α=0.5-1. However, at higher frequencies flux noise is observed to increase with Ohmic (∝ω) [1] or super-Ohmic (∝ω3) [2] frequency dependence. While the low frequency behaviour can be explained by assuming a distribution of interacting impurities with magnetic moments (spins), the high-frequency behaviour remains a puzzle [3].
We describe a mechanism of flux noise that originates from the presence of quasiparticles in the superconducting wires, and predict the resulting frequency and temperature dependence. Under the assumption of thermal equilibrium for the quasiparticles, flux noise is shown to originate from Johnson-Nyquist fluctuations due to the quasiparticle surface resistance [4]. At low frequencies, the latter is much lower than the typical residual resistance observed in experiments, thus leading to white flux noise. However, at higher frequencies ħω » kBT the thermal quasiparticles generate Ohmic flux noise (∝ω). We discuss the impact of a nonequilibrium distribution of quasiparticles and compare our results to experiments available to date.
[1] T. Lanting et Al, Phys. Rev. B 83, 180502(R) (2011).
[2] C. M. Quintana et Al, Phys. Rev. Lett.118, 057702(R) (2017).
[3] J. A. Nava Aquino and R. de Sousa, Phys. Rev. B 106, 144506 (2022).
[4] D. C. Mattis and J. Bardeen, Phys. Rev. 111, 412 (1958).
We describe a mechanism of flux noise that originates from the presence of quasiparticles in the superconducting wires, and predict the resulting frequency and temperature dependence. Under the assumption of thermal equilibrium for the quasiparticles, flux noise is shown to originate from Johnson-Nyquist fluctuations due to the quasiparticle surface resistance [4]. At low frequencies, the latter is much lower than the typical residual resistance observed in experiments, thus leading to white flux noise. However, at higher frequencies ħω » kBT the thermal quasiparticles generate Ohmic flux noise (∝ω). We discuss the impact of a nonequilibrium distribution of quasiparticles and compare our results to experiments available to date.
[1] T. Lanting et Al, Phys. Rev. B 83, 180502(R) (2011).
[2] C. M. Quintana et Al, Phys. Rev. Lett.118, 057702(R) (2017).
[3] J. A. Nava Aquino and R. de Sousa, Phys. Rev. B 106, 144506 (2022).
[4] D. C. Mattis and J. Bardeen, Phys. Rev. 111, 412 (1958).
* This work was supported by NSERC (Canada) through its Discovery program (Grant No. RGPIN-2020-04328).
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Publication: We are planning to publish these results later this year.
Presenters
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Jose Alberto Nava Aquino
University of Victoria
Authors
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Jose Alberto Nava Aquino
University of Victoria
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Rogério de Sousa
Department of Physics and Astronomy, University of Victoria, University of Victoria