 Basic measurement

A rank-one projective measurement associated with an orthonormal basis $\{|b_j⟩{\}}_j$. For a density matrix $\rho$, outcome $j$ has probability $⟨b_j|\rho |b_j⟩$ and leaves the measured system in the pure state $|b_j⟩$ whenever that probability is nonzero. It can be implemented by mapping this orthonormal basis to the computational basis with a unitary transformation and performing a computational-basis measurement.^[ref]