[ALPS-users] Question about measurements in the MPS code

Dear all,

I'm not sure about something concerning the measurements in the MPS code. For instance, I consider the one-dimensional Bose-Hubbard model and then I measure the density-density correlations by the following line : model['MEASURE_CORRELATIONS[Density-density correlations]'] = 'n:n'. As an output, I get a vector of L*L - L components with L the number of sites (I agree due to the fact that we don't have access to the <n_i n_j> values where the index 'i' is equal to 'j', we have to define a new operator n^2) but I haven't seen in the doc how this vector is organized. More precisely, which index is modify first? Do we have something like : d.y[0][:] = (<n0n1>, <n0n2>, ...,<n0,NL-1>, <n1n0>, <n1n2>, ...) .

Thanks in advance,

Julien