Fig. 5: Echo sequence.
a, Bloch sphere representation of the odd-parity two-spin subspace, indicating the rotation axes, \({\widehat{Z}}^{{\prime} }\) and \({\widehat{X}}^{{\prime} }\) and their angular deviation (θZ, θX) from the nominal \(\widehat{Z}\) axis defined by \(\left|\text{S}\right\rangle\) and \(\left|\text{T}_{0}\right\rangle\). b, Schematic of the exchange echo sequence. c, Echo signal data (purple dots) as a function of free evolution time difference τ2 − τ1, fitted with a decay envelope (orange line) with amplitude Aecho. d, Echo amplitude as a function of total free evolution time τ1 + τ2 where τ2 = τ1. The data (purple dots) were fitted with an exponential decay (dashed orange line). Error bars indicate the standard deviation of the fitted Aecho data.
