[ALPS-users] [help] How to compute the expectation value of 4 operators( two creation and two destruction operators)

Hello all, I have been trying to compute the expectation value of cdag(1) c(2) cdag(3) c(4) where two creation and two destruction operators are involved and 1, 2 ,3 and 4 label the sites in a spinless Hubbard model. Could anyone kindly tell me how I should define this in the parameter file or in the models.xml? Thanks a lot! Best, Jun