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Properties of multi-partite dark states
Kok, Pieter; Nemoto, Kae; Munro, William J.
Keyword(s): charactersation of entanglement; entanglement manipulation; mixed states
Abstract: We investigate and define dark and semi-dark states for multiple qudit systems. For two level systems semi-dark and dark states are equivalent. We show that the semi-dark states are equivalent to the singlet states of the rotation group. They exist for many multiple qudit systems, whereas dark states are quite rare. We then show that when a dark state is collapsed onto another dark state of fewer parties, the resulting state is again dark. Also one can use two orthogonal multi-qudit dark states to construct a decoherence-free qudit. Notes: Pieter Kok, Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 126-347, 4800 Oak Grove Drive, Pasadena, California 91109-8099, USA. Kae Nemoto, School of Informatics, Dean Street, University of Wales, Bangor, LL57 1UT, UK
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