conservation_law bug
The following code produces a system which should obey the conservation law I entered.
import kwant
import numpy as np
s0 = np.array([[1., 0.], [0., 1.]])
sx = np.array([[0., 1.], [1., 0.]])
sz = np.array([[1., 0.], [0., -1.]])
s0sz = np.kron(s0, sz)
sxsz = np.kron(sx, sz)
lat = kwant.lattice.chain(norbs=4)
syst = kwant.Builder(conservation_law=-s0sz)
syst[lat(0)] = sxsz
syst = syst.finalized()
syst.discrete_symmetry().validate(syst.hamiltonian_submatrix())