Fig. 4

Noise analyses. a T₂ vs number of π-pulses from measurements with Carr–Purcell–Meiboom–Gill sequences (datum with black cross for Hahn-echo, data with blue/green crosses for 2^1–9 π-pulses, exponential fit with red line, exponent n = 0.05 ± 0.01). b Noise spectrum extracted from the same measurements as in a (starting from 2¹ pulses, data with blue/green dots, Lorentzian fit with red line, correlation time τ_c fixed to represent the highest probed frequency). The Larmor frequencies of several nuclear spins are indicated (grey dashed lines); B = 1.8 mT. c Single quantum (data with blue crosses, exponential-decay fit with red line, measured \(T_1^{{\mathrm{SQ}}}\) ≈ 7.4 ms) and double quantum (data with cyan circles, exponential-decay fit with orange line, measured \(T_1^{{\mathrm{DQ}}}\) ≈ 3.4 ms) T₁ measurements for estimating relaxation rates Ω (1/\(T_1^{{\mathrm{SQ}}}\) = 3Ω) and γ (1/\(T_1^{{\mathrm{DQ}}}\) = Ω + 2γ), which are illustrated in the inset