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Quantum control of the motional states of trapped ions through fast switching of trapping potentials
(2013)New Journal of PhysicsWe propose a new scheme for supplying voltages to the electrodes of microfabricated ion traps, enabling access to a regime in which changes to the trapping potential are made on timescales much shorter than the period of the secular oscillation frequencies of the trapped ions. This opens up possibilities for speeding up the transport of ions in segmented ion traps and also provides access to control of multiple ions in a string faster ...Journal Article -
Cyclic depopulation of edge states in a large quantum dot
(2013)New Journal of PhysicsWe investigate the magneto-transport through a 1.6 μm wide quantum dot (QD) with an adjacent charge detector, for different integer filling factors in the QD and constrictions. When this system is operated at a high transmission, it acts as a Fabry–Pérot interferometer, where transport is governed by a Coulomb blockade mechanism. For lower transmissions where the barriers are in the tunneling regime, we can directly measure the charge ...Journal Article -
DebtRank: Too Central to Fail?
(2012)Scientific ReportsSystemic risk, here meant as the risk of default of a large portion of the financial system, depends on the network of financial exposures among institutions. However, there is no widely accepted methodology to determine the systemically important nodes in a network. To fill this gap, we introduce, DebtRank, a novel measure of systemic impact inspired by feedback-centrality. As an application, we analyse a new and unique dataset on the ...Journal Article -
Electron flow in split-gated bilayer graphene
(2012)New Journal of PhysicsWe present transport measurements on a bilayer graphene sheet with a homogeneous back gate and a split top gate. The electronic transport data indicate the capability of directing electron flow through bilayer graphene nanostructures purely defined by electrostatic gating. Comparing the transconductance data recorded for different top gate geometries—continuous barrier and split gate—the observed transport features for the split gate can ...Journal Article -
Exciton-assisted optomechanics with suspended carbon nanotubes
(2012)New Journal of PhysicsWe propose a framework for inducing strong optomechanical effects in a suspended carbon nanotube based on deformation potential (DP) exciton–phonon coupling. The excitons are confined using an inhomogeneous axial electric field which generates optically active quantum dots with a level spacing in the milli-electronvolt range and a characteristic size in the 10 nm range. A transverse field induces a tunable parametric coupling between the ...Journal Article -
Rydberg state creation by tunnel ionization
(2013)New Journal of PhysicsIt is well known from numerical and experimental results that the fraction of Rydberg states (excited neutral atoms) created by tunnel ionization declines dramatically with increasing ellipticity of laser light, in a way that is similar to high harmonic generation (HHG). We present a method to analyze this dependence on ellipticity, deriving a probability distribution of Rydberg states that agrees closely with experimental (Nubbemeyer et ...Journal Article -
Interference of electrons in backscattering through a quantum point contact
(2013)New Journal of PhysicsScanning gate microscopy is used to locally investigate electron transport in a high-mobility two-dimensional electron gas formed in a GaAs/AlGaAs heterostructure. Using quantum point contacts, we observe branches caused by electron backscattering decorated with interference fringes similar to previous observations by Topinka et al (2000 Science 289 2323). We investigate the branches at different points of a conductance plateau as well ...Journal Article -
Tunable charge detectors for semiconductor quantum circuits
(2013)New Journal of PhysicsNanostructures defined in high-mobility two-dimensional electron systems offer a unique way of controlling the microscopic details of the investigated device. Quantum point contacts play a key role in these investigations, since they are not only a research topic themselves, but also turn out to serve as convenient and powerful detectors for their electrostatic environment. We investigate how the sensitivity of charge detectors can be ...Journal Article -
Holonomic quantum computing in symmetry-protected ground states of spin chains
(2013)New Journal of PhysicsWhile solid-state devices offer naturally reliable hardware for modern classical computers, thus far quantum information processors resemble vacuum tube computers in being neither reliable nor scalable. Strongly correlated many body states stabilized in topologically ordered matter offer the possibility of naturally fault tolerant computing, but are both challenging to engineer and coherently control and cannot be easily adapted to different ...Journal Article -
Intrinsic noise alters the frequency spectrum of mesoscopic oscillatory chemical reaction systems
(2011)Scientific ReportsMesoscopic oscillatory reaction systems, for example in cell biology, can exhibit stochastic oscillations in the form of cyclic random walks even if the corresponding macroscopic system does not oscillate. We study how the intrinsic noise from molecular discreteness influences the frequency spectrum of mesoscopic oscillators using as a model system a cascade of coupled Brusselators away from the Hopf bifurcation. The results show that the ...Journal Article