Fig. 1: Noise and decoherence from microscopic defects and adsorbates.

a Schematic of treatments and impacted surfaces. b Spectral sensitivity of qubit noise measurements: δΓ₁ and δf₀₁ denote low-frequency parameter fluctuations as measured by the widths of long-term Γ₁ and f₀₁ histograms. \({{{\Gamma }}}_{2}^{* }\) probes frequency fluctuations over the full Ramsey averaging time whereas Hahn, and CPMG echo sequences probe noise only above a cut-off frequency. S_Φ,1/f and S_ϕ,BB denote 1/f and broadband flux-noise powers extracted from the flux dependence of \({{{\Gamma }}}_{2}^{{{{\rm{e}}}}}\). Rabi decay probes noise at the qubit Rabi frequency and Γ₁ spectroscopy are sensitive to noise at the qubit frequency. c Image of the UHV package that can be used to load two-qubit chips in a controlled environment.