Multiphoton Stokes-parameter invariant for entangled states
Gregg S. Jaeger, Mihail Teodorescu-Frumosu, Alexander V. Sergienko, Bahaa E. A. Saleh, Malvin Carl Teich · Physical Review A · 2003
We consider the Minkowskian norm of the n-photon Stokes tensor, a scalar invariant under the group realized by the transformations of stochastic local quantum operations and classical communications (SLOCC). This invariant is offered as a candidate entanglement measure for n-qubit states and discussed in relation to measures of quantum state entanglement for certain important classes of two-qubit and three-qubit systems. This invariant can be directly estimated via a quantum network, obviating the need to perform laborious quantum state tomography. We also show that this invariant directly captures the extent of entanglement purification due to SLOCC filters.