title: Qubit channels can require more than two inputs to achieve capacity.
abstract: We give examples of qubit channels that require three input states in order to achieve the Holevo capacity.
authors.affiliation: Department of Mathematics, Northeastern University, Boston, Massachusetts 02115, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: King
authors.forename: Michael
authors.initials: M
authors.lastname: Nathanson
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Ruskai