Local Conversion of Greenberger-Horne-Zeilinger States to Approximate W States
Philip John Walther, Katharina Resch, Anton Zeilinger · Physical Review Letters · 2005
Genuine 3-qubit entanglement comes in two different inconvertible types represented by the Greenberger-Horne-Zeilinger (GHZ) state and the $W$ state. We describe a specific method based on local positive operator valued measures and classical communication that can convert the ideal $N$-qubit GHZ state to a state arbitrarily close to the ideal $N$-qubit $W$ state. We then experimentally implement this scheme in the 3-qubit case and characterize the input and the final state using 3-photon quantum state tomography.