  We propose an experimental scheme for the measurement of entanglement between
two two-level atoms. Our scheme requires one of the two entangled atoms to
interact with a cavity field dispersively, and we show that by measuring the
zero time-delay second-order coherence function of the cavity field, one can
measure the concurrence of an arbitrary Bell-like atomic two-qubit state. As
our scheme requires only one of the atoms to interact with the measured cavity,
the entanglement quantification becomes independent of the location of the
other atom. Therefore, our scheme can have important implications for
entanglement quantification in distributed quantum systems.

Quantum Physics