2,318 research outputs found
Radio-frequency operation of a double-island single-electron transistor
We present results on a double-island single-electron transistor (DISET)
operated at radio-frequency (rf) for fast and highly sensitive detection of
charge motion in the solid state. Using an intuitive definition for the charge
sensitivity, we compare a DISET to a conventional single-electron transistor
(SET). We find that a DISET can be more sensitive than a SET for identical,
minimum device resistances in the Coulomb blockade regime. This is of
particular importance for rf operation where ideal impedance matching to 50 Ohm
transmission lines is only possible for a limited range of device resistances.
We report a charge sensitivity of 5.6E-6 e/sqrt(Hz) for a rf-DISET, together
with a demonstration of single-shot detection of small (<=0.1e) charge signals
on microsecond timescales.Comment: 6 pages, 6 figure
Optically thin clouds in the trades
We develop a new method to describe the total cloud cover including optically thin clouds in trade wind cumulus cloud fields. Climate models and large eddy simulations commonly underestimate the cloud cover, while estimates from observations largely disagree on the cloud cover in the trades. Currently, trade wind clouds significantly contribute to the uncertainty in climate sensitivity estimates derived from model perturbation studies. To simulate clouds well, especially how they change in a future climate, we have to know how cloudy it is.In this study we develop a method to quantify the cloud cover from a cloud-free perspective. Using well-known radiative transfer relations we retrieve the cloud-free contribution in high-resolution satellite observations of trade cumulus cloud fields during EUREC4A. Knowing the cloud-free part, we can investigate the remaining cloud-related contributions consisting of areas detected by common cloud-masking algorithms and undetected areas related to optically thin clouds. We find that the cloud-mask cloud cover underestimates the total cloud cover by 33 %. Aircraft lidar measurements support our findings by showing a high abundance of optically thin clouds during EUREC4A. Mixing the undetected optically thin clouds into the cloud-free signal can cause an underestimation of the cloud radiative effect of up to −7.5 %. We further discuss possible artificial correlations in aerosol–cloud cover interaction studies that might arise from undetected optically thin low clouds. Our analysis suggests that the known underestimation of trade wind cloud cover and simultaneous overestimation of cloud brightness in models are even higher than assumed so far
Parity measurement of one- and two-electron double well systems
We outline a scheme to accomplish measurements of a solid state double well
system (DWS) with both one and two electrons in non-localised bases. We show
that, for a single particle, measuring the local charge distribution at the
midpoint of a DWS using an SET as a sensitive electrometer amounts to
performing a projective measurement in the parity (symmetric/antisymmetric)
eigenbasis. For two-electrons in a DWS, a similar configuration of SET results
in close-to-projective measurement in the singlet/triplet basis. We analyse the
sensitivity of the scheme to asymmetry in the SET position for some
experimentally relevant parameter, and show that it is realisable in
experiment.Comment: 18 Pages, to appear in PR
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The Moon at thermal infrared wavelengths: A benchmark for asteroid thermal models
Thermal-infrared measurements of asteroids are crucial for deriving the
objects' sizes, albedos, and also the thermophysical properties of the surface
material. Depending on the available data, a range of simple to complex thermal
models are applied to achieve specific science goals. However, testing these
models is often a difficult process and the uncertainties of the derived
parameters are not easy to estimate. Here, we make an attempt to verify a
widely accepted thermophysical model (TPM) against unique thermal infrared
(IR), full-disk, and well-calibrated measurements of the Moon. The data were
obtained by the High-resolution InfraRed Sounder (HIRS) instruments on board a
fleet of Earth weather satellites that serendipitously scan over the Moon. We
found 22 Moon intrusions, taken in 19 channels between 3.75 micron and 15.0
micron, and over a wide phase angle range from -73.1 deg to +73.8 deg. The
similarity between these Moon data and typical asteroid spectral-IR energy
distributions allows us to benchmark the TPM concepts and to point out
problematic aspects. The TPM predictions match the HIRS measurements within 5%
(10% at the shortest wavelengths below 5 micron when using the Moon's known
properties (size, shape, spin, albedo, thermal inertia, roughness) in
combination with a newly established wavelength-dependent hemispherical
emissivity. In the 5-7.5 micron and in the 9.5 to 11 micron ranges, the global
emissivity model deviates considerably from the known lunar sample spectra. Our
findings will influence radiometric studies of near-Earth and main-belt
asteroids in cases where only short-wavelength data (from e.g., NEOWISE, the
warm Spitzer mission, or ground-based M-band measurements) are available. The
new, full-disk IR Moon model will also be used for the calibration of IR
instrumentation on interplanetary missions (e.g., for Hayabusa-2) and weather
satellites.Comment: 21 pages, 9 figures, 7 tables, accepted for publication in Astronomy
& Astrophysics in March 202
Observing sub-microsecond telegraph noise with the radio frequency single electron transistor
Telegraph noise, which originates from the switching of charge between
meta-stable trapping sites, becomes increasingly important as device sizes
approach the nano-scale. For charge-based quantum computing, this noise may
lead to decoherence and loss of read out fidelity. Here we use a radio
frequency single electron transistor (rf-SET) to probe the telegraph noise
present in a typical semiconductor-based quantum computer architecture. We
frequently observe micro-second telegraph noise, which is a strong function of
the local electrostatic potential defined by surface gate biases. We present a
method for studying telegraph noise using the rf-SET and show results for a
charge trap in which the capture and emission of a single electron is
controlled by the bias applied to a surface gate.Comment: Accepted for publication in Journal of Applied Physics. Comments
always welcome, email [email protected], [email protected]
Development and operation of the twin radio frequency single electron transistor for solid state qubit readout
Ultra-sensitive detectors and readout devices based on the radio frequency
single electron transistor (rf-SET) combine near quantum-limited sensitivity
with fast operation. Here we describe a twin rf-SET detector that uses two
superconducting rf-SETs to perform fast, real-time cross-correlated
measurements in order to distinguish sub-electron signals from charge noise on
microsecond time-scales. The twin rf-SET makes use of two tuned resonance
circuits to simultaneously and independently address both rf-SETs using
wavelength division multiplexing (WDM) and a single cryogenic amplifier. We
focus on the operation of the twin rf-SET as a charge detector and evaluate the
cross-talk between the two resonance circuits. Real time suppression of charge
noise is demonstrated by cross correlating the signals from the two rf-SETs.
For the case of simultaneous operation, the rf-SETs had charge sensitivities of
and .Comment: Updated version, including new content. Comments most welcome:
[email protected] or [email protected]
Modeling Single Electron Transfer in Si:P Double Quantum Dots
Solid-state systems such as P donors in Si have considerable potential for
realization of scalable quantum computation. Recent experimental work in this
area has focused on implanted Si:P double quantum dots (DQDs) that represent a
preliminary step towards the realization of single donor charge-based qubits.
This paper focuses on the techniques involved in analyzing the charge transfer
within such DQD devices and understanding the impact of fabrication parameters
on this process. We show that misalignment between the buried dots and surface
gates affects the charge transfer behavior and identify some of the challenges
posed by reducing the size of the metallic dot to the few donor regime.Comment: 11 pages, 7 figures, submitted to Nanotechnolog
Self-aligned fabrication process for silicon quantum computer devices
We describe a fabrication process for devices with few quantum bits (qubits),
which are suitable for proof-of-principle demonstrations of silicon-based
quantum computation. The devices follow the Kane proposal to use the nuclear
spins of 31P donors in 28Si as qubits, controlled by metal surface gates and
measured using single electron transistors (SETs). The accurate registration of
31P donors to control gates and read-out SETs is achieved through the use of a
self-aligned process which incorporates electron beam patterning, ion
implantation and triple-angle shadow-mask metal evaporation
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