Measurable genuine tripartite entanglement of ($2\otimes 2\otimes   n$)-dimensional quantum states via only two simultaneous copies
  Usually, the three-tangle of a tripartite pure state of qubits can be directly measured with the simultaneous preparation of a not-less-than-four-fold copy of the state. We show that the exact genuine tripartite entanglement for ($2\otimes2\otimes n$)-dimensional pure quantum states can be measured in a similar manner, provided that only two simultaneous copies of the state are available. Lower bounds are also proposed for more convenient experimental operations. As an example, a comprehensive demonstration of the scheme is provided for the three-tangle of a three-qubit state. 
Chang-shui Yu, Bao-qing Guo, Si-ren Yang
quant-ph