  Dipole-dipole interaction is a long-range interaction, hence we could expect
that the self-consistent field approximation might be applied. In most cases it
is correct, but dipolar BECs reveal a surprise. Structure of the
self-consistent field term requires that interacting particles are in different
quantum states, while in BECs all particles in a single quantum state. This
fact requires to consider the two-particle polarisation, which describes
dipole-dipole interaction, in more details. We present this consideration and
show an astonishing result that the two-particle quantum correlation in dipolar
BECs reveals in the same form as the self-consistent field term.
