Hi. I'm trying to prove that
[\Omega] = \int dq \int dp \, \rho_{w}(q,p)\,\Omega_{w}(q,p)
where
\rho_{w}(q,p) = \frac{1}{2\pi\hbar} \int dy \, \langle q-\frac{y}{2}|\rho|q+\frac{y}{2}\rangle\,\exp(i\frac{py}{\hbar})
is the Wigner function, being \rho a density matrix. On the other hand...