Figure 1

Negativity volume \({\mathscr{V}}\) of the Wigner function of the diagonal mixed qubit state \({\hat{\rho }}_{d}^{q}\) (blue solid curve), given in Eq. (13), as a function of the parameter a. The negativity volume \({\mathscr{V}}\) of the Wigner function of the pure qubit state \(|q\rangle \), given in Eq. (10), is shown by red dotted line.