title: Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses.
abstract: The nuclear spins in nanostructured semiconductors play a central role in quantum applications. The nuclear spins represent a useful resource for generating local magnetic fields but nuclear spin noise represents a major source of dephasing for spin qubits. Controlling the nuclear spins enhances the resource while suppressing the noise. NMR techniques are challenging: the group III and V isotopes have large spins with widely different gyromagnetic ratios; in strained material there are large atom-dependent quadrupole shifts; and nanoscale NMR is hard to detect. We report NMR on 100,000 nuclear spins of a quantum dot using chirped radiofrequency pulses. Following polarization, we demonstrate a reversal of the nuclear spin. We can flip the nuclear spin back and forth a hundred times. We demonstrate that chirped NMR is a powerful way of determining the chemical composition, the initial nuclear spin temperatures and quadrupole frequency distributions for all the main isotopes. The key observation is a plateau in the NMR signal as a function of sweep rate: we achieve inversion at the first quantum transition for all isotopes simultaneously. These experiments represent a generic technique for manipulating nanoscale inhomogeneous nuclear spin ensembles and open the way to probe the coherence of such mesoscopic systems.
authors.affiliation: Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Munsch
authors.affiliation: Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Gunter
authors.initials: G
authors.lastname: Wüst
authors.affiliation: Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Andreas V
authors.initials: AV
authors.lastname: Kuhlmann
authors.affiliation: Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Fei
authors.initials: F
authors.lastname: Xue
authors.affiliation: 1] Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland [2] Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
authors.forename: Arne
authors.identifier: 0000000228717789
authors.initials: A
authors.lastname: Ludwig
authors.affiliation: 1] Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany [2] Department Physik, Universität Paderborn, Warburger Strasse 100, D-33098 Paderborn, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Reuter
authors.affiliation: Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Wieck
authors.affiliation: Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Martino
authors.identifier: 000000025327051X
authors.initials: M
authors.lastname: Poggio
authors.affiliation: Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Warburton