Normalization in the entanglement calculation.

I think it might be a good idea to describe the convention that was used in the von Neumann entropy calculation. The flag density is True by default in _ent_entropy (lattice.py). This causes a division of the von Neumann entropy by N_A or N_B.

Also the example at https://github.com/weinbe58/QuSpin/blob/master/examples/notebooks/BHM.ipynb additionally divides the entanglement entropy by L

Sent=basis.ent_entropy(V[:,0],sub_sys_A=subsystem)['Sent_A']/L

I (and probably some other people too) are used to different conventions so it would be helpful if the convention was explained in the doc string (a reference to a paper according to which the von Neumann entropy was implemented would be perfectly sufficient too).

I am overall really enjoying working with quspin. It’s a great software package!

[mgbukov]

Hey Benedikt,

thanks a lot for pointing this out! Indeed, I noticed myself some time ago that the density optional argument is not listed, and I made the change in the branch floquet_update. When we merge it into dev_0.3.0 and master this will appear.

I missed the BHM jupyter notebook though. I will change this right away (also in the same branch, to be consistent). Good catch!

I guess by convention for the entanglement you mean the ordering of the basis vectors? Or can u give a bit more details?

@weinbe58 : Phil, the 'densityoptional argument is absent from thetensor_basisand thephoton_basis`. It’s also not present in the documentation, so this is consistent. The Q is whether we want to put it in?

[mgbukov]

This is fixed and the online doc has been updated.