stacked qc mpo for larger scale qc calculation

[jiangtong1000]

This PR is a follow up of #154
Could improve the qc speed. The qc mpo is added by N smaller mpos with bond dim of O(N).

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01% 🎉

Comparison is base (b10fcaf) 84.82% compared to head (d24e8c9) 84.84%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #163      +/-   ##
==========================================
+ Coverage   84.82%   84.84%   +0.01%     
==========================================
  Files         105      105              
  Lines       10207    10232      +25     
==========================================
+ Hits         8658     8681      +23     
- Misses       1549     1551       +2     

Files Changed	Coverage Δ
renormalizer/model/h_qc.py	98.30% <100.00%> (+0.28%)	⬆️
renormalizer/mps/tests/test_gs.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[liwt31]

Looks great! Is it reported in the literature? And how fast is it for typical cases?

[jiangtong1000]

Looks great! Is it reported in the literature? And how fast is it for typical cases?

yea I think this is a well known trick, see Eq 6 of (https://arxiv.org/abs/1703.04789)

[jiangtong1000]

@liwt31 I did not test with typical systems yet, but in principle I think it can speed up N times? if we consider the step of updating the Environment