Cross-spectra correlation matrices computed from Eq. (B.2) for the SIM1 data set in the multipole bin centered at ℓ = 100. Upper panel: correlation matrix computed from the cross-spectra as defined in Eq. (B.1). Middle panel: correlation matrix computed for our toy-model of the correlation presented in Appendix B.2. Bottom panel: correlation matrix computed from the cross-spectra as defined in Eq. (B.6).