Suppressing low-frequency charge noise in superconducting resonators by surface spin desorption

Noise and decoherence due to spurious two-level systems (TLS) located at material interfaces are long-standing issues for quantum devices such as superconducting qubits and ion traps where TLS on nearby surfaces can result in... [ view full abstract ]

Noise and decoherence due to spurious two-level systems (TLS) located at material interfaces are long-standing issues for quantum devices such as superconducting qubits and ion traps where TLS on nearby surfaces can result in noise and excess heating, respectively. For the scaling-up of quantum technologies it is thus crucial to gain a better understanding of the chemical and physical nature of TLS and develop methods for mitigating their effects.  We have previously studied the dynamics of surface TLS by measuring loss and 1/f noise in superconducting resonators [1]. Micro-Electron Spin Resonance (micro-ESR) was also shown [2] to be an efficient tool for identifying the chemical nature of dilute surface spins, believed to be the origin of flux noise in e.g. superconducting qubits.

Here [3] we have used all these methods: by combining measurement of dielectric loss and frequency noise (fig. 1: power spectral density vs. average number of photons in the resonator) with on-chip micro-ESR before and after thermal annealing (fig. 2: ESR spectra before and after annealing) we show that desorption of surface spins is accompanied by an almost tenfold reduction in the charge-induced frequency noise in a superconducting resonator.

These measurements not only reveal the chemical signatures of adsorbed magnetic moments but also highlights their role in generating charge (dielectric) noise in solid state quantum devices, and thus provides a powerful diagnostic tool.

[1] “Evidence for interacting two-level systems from the 1/f noise of a superconducting resonator”
J. Burnett, L. Faoro, I. Wisby, V.L. Gurtovoi, A.V. Chernykh, G.M. Mikhailov, V.A. Tulin, R. Shaikhaidarov, V. Antonov, P.J. Meeson, A.Ya Tzalenchuk and T. Lindström. Nature communications, 5 (2014) 4119

[2] “Direct Identification of Dilute Surface Spins on Al2O3: Origin of Flux Noise in Quantum Circuits”
S.E. de Graaf , A.A. Adamyan AA, T. Lindström, D. Erts, S.E. Kubatkin, A. Ya. Tzalenchuk , A.V Danilov. Physical review letters 118(5):057703 (2017).

[3] “Suppression of 1/f noise in solid state quantum devices by surface spin desorption” 
S.E.  de Graaf, L . Faoro,  J. Burnett, A.A.  Adamyan, A.Ya.  Tzalenchuk, S.E.  Kubatkin, T. Lindström and A.V. Danilov.  Nature Communications 9 (2018) 1143