title: Process tomography of ion trap quantum gates.
abstract: A crucial building block for quantum information processing with trapped ions is a controlled-NOT quantum gate. In this Letter, two different sequences of laser pulses implementing such a gate operation are analyzed using quantum process tomography. Fidelities of up to 92.6(6)% are achieved for single-gate operations and up to 83.4(8)% for two concatenated gate operations. By process tomography we assess the performance of the gates for different experimental realizations and demonstrate the advantage of amplitude-shaped laser pulses over simple square pulses. We also investigate whether the performance of concatenated gates can be inferred from the analysis of the single gates.
authors.affiliation: Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Riebe
authors.forename: K
authors.initials: K
authors.lastname: Kim
authors.forename: P
authors.initials: P
authors.lastname: Schindler
authors.forename: T
authors.initials: T
authors.lastname: Monz
authors.forename: P O
authors.initials: PO
authors.lastname: Schmidt
authors.forename: T K
authors.initials: TK
authors.lastname: Körber
authors.forename: W
authors.initials: W
authors.lastname: Hänsel
authors.forename: H
authors.initials: H
authors.lastname: Häffner
authors.forename: C F
authors.initials: CF
authors.lastname: Roos
authors.forename: R
authors.initials: R
authors.lastname: Blatt