Proposal for direct measurement of concurrence via visibility in a   cavity QED system
  An experimental scheme is proposed that allows direct measurement of the concurrence of a two-qubit cavity system. It is based on the cavity-QED technology using atoms as flying qubits and relies on the identity of the two-particle visibility of the atomic probability with the concurrence of the cavity system. The scheme works for any arbitrary pure initial state of the two-qubit cavity system. 
Sang Min Lee, Se-Wan Ji, Hai-Woong Lee, and M. Suhail Zubairy