Hello, I probably know the answer to this already, but just wanted to check: I would like to use the Montecarlo code to simulate a system with a Hamiltonian that has the Sy operator, that is Sy=-I/2(Splus-Sminus). The worm and sse codes return a runtime error "can not convert complex number into real one". If I don't include de I constant (or (0.,1.) ) in the model.xml file the code starts, but then complains that it cannot simulate this term (which without the complex unit is non-Hermitian). I cannot rotate my basis because I also have the Sx operator, so I am stuck with Sy. Is there a way to do this? It looks like a no-no... Thanks Fernando -- ============================== Fernando Cucchietti Research Fellow ICFO-Institut de Ciencies Fotoniques Mediterranean Technology Park Av. Canal Olimpic s/n 08860 Castelldefels (Barcelona), Spain ============================== 1+1=3, for large values of 1 ------------------------------