Zero-Error Communication via Quantum Channels, Noncommutative Graphs, and a Quantum Lovász Number

Runyao Duan,1, 2 Simone Severini,3 and Andreas Winter4, 5 Centre for Quantum Computation and Intelligent Systems (QCIS), Faculty of Engineering and Information Technology, University of Technology, Sydney NSW2007, Australia State Key Laboratory of Intelligent Technology and Systems, Tsinghua National Laboratory for Information Science and Technology, Department of Computer Science and Technology, Tsinghua University, Beijing 100084, China Department of Physics and Astronomy, University College London, WC1E 6BT London, U.K. Department of Mathematics, University of Bristol, Bristol BS8 1TW, U.K. Centre for Quantum Technologies, National University of Singapore, 2 Science Drive 3, Singapore 117542∗ (Dated: 11 March 2010)