How can we find a Wigner function for the four maximally entangled Bell states $(|00\rangle \pm |11\rangle)/\sqrt{2}$, $(|01\rangle \pm |10\rangle)/\sqrt{2}$?
I have used the basis where labels for each qubit are $\sigma_x$ and $\sigma_z$ eigenvalues. The thing is that I have first expressed the two-qubit density matrix in terms of tensor product of Pauli matrices however I am not able to proceed how to proceed further.
