title: Experimental Schmidt decomposition and state independent entanglement detection.
abstract: We introduce an experimental procedure for the detection of quantum entanglement of an unknown quantum state with a small number of measurements. The method requires neither a priori knowledge of the state nor a shared reference frame between the observers and can thus be regarded as a perfectly state-independent entanglement witness. The scheme starts with local measurements, possibly supplemented with suitable filtering, which essentially establishes the Schmidt decomposition for pure states. Alternatively we develop a decision tree that reveals entanglement within few steps. These methods are illustrated and verified experimentally for various entangled states of two and three qubits.
authors.affiliation: Institute of Theoretical Physics and Astrophysics, University of Gdańsk, PL-80-952 Gdańsk, Poland.
authors.forename: Wiesław
authors.initials: W
authors.lastname: Laskowski
authors.forename: Daniel
authors.initials: D
authors.lastname: Richart
authors.forename: Christian
authors.initials: C
authors.lastname: Schwemmer
authors.forename: Tomasz
authors.initials: T
authors.lastname: Paterek
authors.forename: Harald
authors.initials: H
authors.lastname: Weinfurter