Calculation of Dynamical Lie Algebra

Hello,

I am currently using the lie_closure function to compute the DLA. Unfortunately, I encounter an error when using these generators for 4 qubits (it works for 1 and 2 qubits)

generators = [Z(i) for i in range(n)]
generators += [Y(i) for i in range(n)]
generators += [(I(i)-Z(i))@(I(i+1)-X(i+1)) for i in range(n-1)] #generator of CNOT gate

The error is: LinAlgError: Singular matrix.

What does this error mean in the context of DLA elements?