title: Quadrupolar and anisotropy effects on dephasing in two-electron spin qubits in GaAs.
abstract: Understanding the decoherence of electron spins in semiconductors due to their interaction with nuclear spins is of fundamental interest as they realize the central spin model and of practical importance for using them as qubits. Interesting effects arise from the quadrupolar interaction of nuclear spins with electric field gradients, which have been shown to suppress diffusive nuclear spin dynamics and might thus enhance electron spin coherence. Here we show experimentally that for gate-defined GaAs quantum dots, quadrupolar broadening of the nuclear Larmor precession reduces electron spin coherence by causing faster decorrelation of transverse nuclear fields. However, this effect disappears for appropriate field directions. Furthermore, we observe an additional modulation of coherence attributed to an anisotropic electronic g-tensor. These results complete our understanding of dephasing in gated quantum dots and point to mitigation strategies. They may also help to unravel unexplained behaviour in self-assembled quantum dots and III-V nanowires.
authors.affiliation: JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Botzem
authors.affiliation: JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany.
authors.forename: Robert P G
authors.initials: RP
authors.lastname: McNeil
authors.affiliation: JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany.
authors.forename: Jan-Michael
authors.initials: JM
authors.lastname: Mol
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Schuh
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg, Germany.
authors.forename: Dominique
authors.initials: D
authors.lastname: Bougeard
authors.affiliation: JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Bluhm