11 research outputs found
Spin-dependent shot noise enhancement in a quantum dot
The spin-dependent dynamical blockade was investigated in a lateral quantum
dot in a magnetic field. Spin-polarized edge channels in the two-dimensional
leads and the spatial distribution of Landau orbitals in the dot modulate the
tunnel coupling of the quantum dot level spectrum. In a measurement of the
electron shot noise we observe a pattern of super-Poissonian noise which is
correlated to the spin-dependent competition between different transport
channels
Dynamik des Transports in Quantenpunktsystemen
[no abstract
A quantized current source with mesoscopic feedback
We study a mesoscopic circuit of two quantized current sources, realized by
non-adiabatic single- electron pumps connected in series with a small
micron-sized island in between. We find that quantum transport through the
second pump can be locked onto the quantized current of the first one by a
feedback due to charging of the mesoscopic island. This is confirmed by a
measurement of the charge variation on the island using a nearby charge
detector. Finally, the charge feedback signal clearly evidences loading into
excited states of the dynamic quantum dot during single-electron pump
operation
Two electrons interacting at a mesoscopic beam splitter
The non-linear response of a beam splitter to the coincident arrival of
interacting particles enables numerous applications in quantum engineering and
metrology yet poses considerable challenge to achieve focused interactions on
the individual particle level. Here we probe the coincidence correlations at a
mesoscopic constriction between individual ballistic electrons in a system with
unscreened Coulomb interactions and introduce concepts to quantify the
associated parametric non-linearity. The full counting statistics of joint
detection allows us to explore the interaction-mediated energy exchange. We
observe an increase from 50\% up to 70\% in coincidence counts between
statistically indistinguishable on demand sources, and a correlation signature
consistent with independent tomography of the electron emission. Analytical
modeling and numerical simulations underpin consistency of the experimental
results with Coulomb interactions between two electrons counterpropagating in a
dispersive quadratic saddle, and demonstrate interactions sufficiently strong,
, to enable single-shot in-flight detection and quantum
logic gates
Partitioning of on-demand electron pairs
We demonstrate the high fidelity splitting of electron pairs emitted on
demand from a dynamic quantum dot by an electronic beam splitter. The fidelity
of pair splitting is inferred from the coincidence of arrival in two detector
paths probed by a measurement of the partitioning noise. The emission
characteristic of the on-demand electron source is tunable from electrons being
partitioned equally and independently to electron pairs being split with a
fidelity of 90%. For low beam splitter transmittance we further find evidence
of pair bunching violating statistical expectations for independent fermions
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Roadmap on quantum nanotechnologies
Quantum phenomena are typically observable at length and time scales smaller than those of our everyday experience, often involving individual particles or excitations. The past few decades have seen a revolution in the ability to structure matter at the nanoscale, and experiments at the single particle level have become commonplace. This has opened wide new avenues for exploring and harnessing quantum mechanical effects in condensed matter. These quantum phenomena, in turn, have the potential to revolutionize the way we communicate, compute and probe the nanoscale world. Here, we review developments in key areas of quantum research in light of the nanotechnologies that enable them, with a view to what the future holds. Materials and devices with nanoscale features are used for quantum metrology and sensing, as building blocks for quantum computing, and as sources and detectors for quantum communication. They enable explorations of quantum behaviour and unconventional states in nano- and opto-mechanical systems, low-dimensional systems, molecular devices, nano-plasmonics, quantum electrodynamics, scanning tunnelling microscopy, and more. This rapidly expanding intersection of nanotechnology and quantum science/technology is mutually beneficial to both fields, laying claim to some of the most exciting scientific leaps of the last decade, with more on the horizon
Shot-noise at a Fermi-edge singularity: Non-Markovian dynamics
For an InAs quantum dot we study the current shot noise at a Fermi-edge singularity in low temperature cross-correlation measurements. In the regime of the interaction effect the strong suppression of noise observed at zero magnetic field and the sequence of enhancement and suppression in magnetic field go beyond a Markovian master equation model. Qualitative and quantitative agreement can however be achieved by a generalized master equation model taking non-Markovian dynamics into account. © 2013 AIP Publishing LLC