  Experimental procedures are presented for the rapid detection of entanglement
of unknown arbitrary quantum states. The methods are based on the entanglement
criterion using accessible correlations and the principle of correlation
complementarity. Our first scheme essentially establishes the Schmidt
decomposition for pure states, with few measurements only and without the need
for shared reference frames. The second scheme employs a decision tree to speed
up entanglement detection. We analyze the performance of the methods using
numerical simulations and verify them experimentally for various states of two,
three and four qubits.
