Calculate the sum of probabilities with the Hashimoto matrix

[LeonidPryadko]

Main question -- what can be done in the case of a hypergraph. Something may be doable for a surface code; big question with more general LDPC codes. Perhaps some tensor contraction protocol would work?

• make it mode=2 with some submode
• Hashimoto matrix construction Q
• Case of k=1. Identify two boundaries to calculate matrix elements with
• Calculate the sum (out| Q^n |in) from n=d and up to some nmax
• Global prefactor correction
• add prefactor calculation for mode=2