title: Fast coherent manipulation of three-electron states in a double quantum dot.
abstract: An important goal in the manipulation of quantum systems is the achievement of many coherent oscillations within the characteristic dephasing time T2(*). Most manipulations of electron spins in quantum dots have focused on the construction and control of two-state quantum systems, or qubits, in which each quantum dot is occupied by a single electron. Here we perform quantum manipulations on a system with three electrons per double quantum dot. We demonstrate that tailored pulse sequences can be used to induce coherent rotations between three-electron quantum states. Certain pulse sequences yield coherent oscillations fast enough that more than 100 oscillations are visible within a T2(*) time. The minimum oscillation frequency we observe is faster than 5 GHz. The presence of the third electron enables very fast rotations to all possible states, in contrast to the case when only two electrons are used, in which some rotations are slow.
authors.affiliation: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Shi
authors.affiliation: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors.forename: C B
authors.initials: CB
authors.lastname: Simmons
authors.affiliation: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Ward
authors.affiliation: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Prance
authors.affiliation: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors.forename: Xian
authors.initials: X
authors.lastname: Wu
authors.affiliation: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors.forename: Teck Seng
authors.initials: TS
authors.lastname: Koh
authors.affiliation: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors.forename: John King
authors.initials: JK
authors.lastname: Gamble
authors.affiliation: Department of Materials Science and Engineering, University of Wisconsin-Madison, 1509 University Avenue, Madison, Wisconsin 53706, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Savage
authors.affiliation: Department of Materials Science and Engineering, University of Wisconsin-Madison, 1509 University Avenue, Madison, Wisconsin 53706, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Lagally
authors.affiliation: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Friesen
authors.affiliation: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors.forename: S N
authors.initials: SN
authors.lastname: Coppersmith
authors.affiliation: Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Eriksson