Extended Data Fig. 7: Coherence characterization in ϵ-CPMG measurements.
From: Quantum thermalization and Floquet engineering in a spin ensemble with a clock transition
a, b, We compare coherence decay profiles as a function of total interrogation time T for two different ϵ-CPMG measurements at ϵ ≈ 0 (yellow) and ϵ ≈ − π/2 (purple). For both cases, the corresponding base sequence has a periodicity of τ + tp, where τ is the free evolution period and tp is the pulse duration, and is repeated k times to advance in time (see the insets). We measure coherence at stroboscopic times T = k(τ + tp). a, τ/2 = 200 ns, tp = 45 ns for ϵ ≈ 0; tp = 25 ns for ϵ ≈ − π/2. b, τ/2 = 50 ns, tp = 43 ns for ϵ ≈ 0; tp = 22 ns for ϵ ≈ − π/2. Experimental data are obtained under the large J condition, and solid lines represent phenomenological stretched exponential fits. To facilitate comparison between the two different ϵ cases, the coherence decay profiles are normalized by their respective maximum coherence values. c, Dependence of ϵ-CPMG sequence coherence on ϵ for the long τ (blue) and short τ (red) cases. When sweeping ϵ, fixed base sequence parameters of (τ/2 = 200 ns, k = 5; blue) and (τ/2 = 50 ns, k = 20; red) are used respectively. Here, all experimental data across different ϵ values are globally normalized by the initial state polarization, ηpol (see Methods and Extended Data Fig. 5d, e). The solid lines denote numerical simulation results using the experimentally calibrated system parameters. The simulated results were globally rescaled to facilitate comparison with the experimental data.
