Hi everyone,

I'm wondering if I can do some calculation with Sy in my spin 1/2 chain. Eventually I enabled COMPLEX to be 1, which sufficed me to have I(1i in matlab) in model xml files. There my H=sum(Sy(i)) for spin 1/2 chain with 4 sites. So the ground state is simply the case when all spin point to y down. Energy -0.5*4=-2 and all site measurements with Sy=-0.5.

The question is that this is perfect with dmrg but not mps_optim, if I just change 'dmrg' in python script to 'mps_optim' <Sy> changes. My result is as follows: dmrg result: [[-0.5 -0.5 -0.5 -0.5]] mps_optim result: [[ 0. +1.54555976e-16j 0. +2.35922393e-16j 0. +9.39602206e-16j 0. +9.38558145e-32j]] Both get identical right energy value -2 but inconsistent in <Sy>. Great complex number result in MPS. Is there something I can do to make it right?

All files are here: https://gitee.com/whitesnow1970/learn-Python-in-alps/tree/master/share

LiuBiao ll070616@126.com