The operator ψ ψ ( x ) annihilates a boson at the point x, while its adjoint ψ ψ † † creates a new boson at the same point. The wavefunction of the Bose–Einstein condensate is then the expectation value ⟨ ⟨ ψ ψ ⟩ ⟩ of ψ ψ ( x ) , which is a classical function that obeys the same equation. The interpretation of the expectation value is that it is the phase that one should give to a newly created boson so that it will coherently superpose with all the other bosons already in the condensate.