  A measurement scheme of atomic qubits pinned at given positions is studied by
analyzing the interference pattern obtained when they emit photons
spontaneously. In the case of two qubits, a well-known relation is revisited,
in which the interference visibility is equal to the concurrence of the state
in the infinite spatial separation limit of the qubits. By taking into account
the super-radiant and sub-radiant effects, it is shown that a state tomography
is possible when the qubit spatial separation is comparable to the wavelength
of the atomic transition. In the case of three qubits, the relations between
various entanglement measures and the interference visibility are studied,
where the visibility is defined from the two-qubit case. A qualitative
correspondence among these entanglement relations is discussed. In particular,
it is shown that the interference visibility is directly related to the maximal
bipartite negativity.
