Hi Miles,

I have a question regarding the MPS in infinite DMRG calculations. When trying to compute the expectation of an operator O, there are two ways of contracting the edge indices, as shown in the figure (please forgive my drawing..)

I think the lower one makes more sense, by definition of MPS, but the upper one is used in the sample codes. Also, the two methods give close but not exactly equal numerical results. Can you explain a little about the (in)equivalence thereof? Thanks!

Best,

Chengshu

Additional "experimental" fact

Thanks for your fast reply. The right orthogonality of the MPS does make the upper one reasonable. But I think it also makes sense to regard the state as "periodic", because when we calculate, say, the correlation function, we simply multiply/contract them together. Also, the states corrsponding to each "Link" index seem to be nicely normalized, see the newly added figure. I can't deduce this result from right orthogonality so I expect itself to be of use. What do you think about this?

Best,

Chengshu