Fock basis ($|n_1,n_2,\dots ⟩$)

An orthonormal basis labelled by the occupations of specified single-particle modes. For one bosonic mode, $|n⟩=(a^{†}{)}^n|0⟩/\sqrt{n!}$ and the number operator has eigenvalue $n$. A coherent state's expansion in this basis gives its overlap and photon-number statistics.