Quantum Information Processing and Quantum Communications

Local Entanglability and Multipartite Entanglement

aula dottorato - Giovedì 28 maggio ore 14.00
  BARBARA KRAUS, University of Innsbruck

>VITAE: Barbara Kraus finished her PhD, entitled "Entanglement Properties of Quantum States and Quantum Operations", at the University of Innsbruck under the supervision of J. Ignacio Cirac. After working for two years at the Max--Planck--Institute for Quantum Optics, Garching, Germany she spent two postdoc years in the group of Nicolas Gisin at the University of Geneva. In 2006 she moved back to Innsbruck, where she is currently working as a senior postdoc in the group of Hans Briegel at the Institute of Theoretical Physics. Her main research interests are the theory of entanglement, quantum optical implementations of quantum information processors, quantum Kolmogorov complexity, quantum computation and simulations, and quantum cryptography.

Barbara Kraus
  We introduce a new, physically motivated, classification of pure quantum states describing n qubits. We characterize all multipartite states which can be maximally entangled to local auxiliary systems using controlled operations. A state has this property iff one can construct out of it an orthonormal basis by applying independent local unitary operations. This implies that those states can be used to encode locally the maximum amount of n independent bits. Examples of these states are the so-called stabilizer states, which are used for quantum error correction and one--way quantum computing. We give a simple characterization of these states and construct a complete set of commuting unitary observables which characterize the state uniquely. Furthermore, we show how these states can be prepared and discuss their applications.

C. Kruszynska and B. Kraus, Multipartite Entanglement and Global Information, arXiv: quant-ph/08083862 (2008), accepted at Phys. Rev. A.