204 research outputs found
Electrically detected magnetic resonance using radio-frequency reflectometry
The authors demonstrate readout of electrically detected magnetic resonance
at radio frequencies by means of an LCR tank circuit. Applied to a silicon
field-effect transistor at milli-kelvin temperatures, this method shows a
25-fold increased signal-to-noise ratio of the conduction band electron spin
resonance and a higher operational bandwidth of > 300 kHz compared to the kHz
bandwidth of conventional readout techniques. This increase in temporal
resolution provides a method for future direct observations of spin dynamics in
the electrical device characteristics.Comment: 9 pages, 3 figure
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]
Bias spectroscopy and simultaneous SET charge state detection of Si:P double dots
We report a detailed study of low-temperature (mK) transport properties of a
silicon double-dot system fabricated by phosphorous ion implantation. The
device under study consists of two phosphorous nanoscale islands doped to above
the metal-insulator transition, separated from each other and the source and
drain reservoirs by nominally undoped (intrinsic) silicon tunnel barriers.
Metallic control gates, together with an Al-AlOx single-electron transistor,
were positioned on the substrate surface, capacitively coupled to the buried
dots. The individual double-dot charge states were probed using source-drain
bias spectroscopy combined with non-invasive SET charge sensing. The system was
measured in linear (VSD = 0) and non-linear (VSD 0) regimes allowing
calculations of the relevant capacitances. Simultaneous detection using both
SET sensing and source-drain current measurements was demonstrated, providing a
valuable combination for the analysis of the system. Evolution of the triple
points with applied bias was observed using both charge and current sensing.
Coulomb diamonds, showing the interplay between the Coulomb charging effects of
the two dots, were measured using simultaneous detection and compared with
numerical simulations.Comment: 7 pages, 6 figure
Magnetoresistance and magnetic breakdown in the quasi-two-dimensional conductors (BEDT-TTF)MHg(SCN)[M=K,Rb,Tl]
The magnetic field dependence of the resistance of
(BEDT-TTF)MHg(SCN)[M=K,Rb,Tl] in the density-wave phase is explained in
terms of a simple model involving magnetic breakdown and a reconstructed Fermi
surface. The theory is compared to measurements in pulsed magnetic fields up to
51 T. The value implied for the scattering time is consistent with independent
determinations. The energy gap associated with the density-wave phase is
deduced from the magnetic breakdown field. Our results have important
implications for the phase diagram.Comment: 5 pages, RevTeX + epsf, 3 figures. To appear in Physical Review B,
Rapid Communications, September 15, 199
Magneto-oscillations in the high-magnetic-field state of (TMTSF)(2)ClO4
We report a systematic study of the anomalous rapid oscillation (RO) phenomena in the quasi-one-dimensional organic metal (TMTSF)(2)ClO4 in pulsed magnetic fields up to 51 T. We argue that the temperature and magnetic-field dependence of the RO amplitudes in the high-field state result from the reconstructed, nested Fermi surface topology at low temperatures in high magnetic fields. In this topology, the RO amplitudes depend on competing magnetic breakdown and Bragg reflection probabilities, along with Lifshitz-Kosevich reduction factors
Allocation mechanisms, incentives, and endemic institutional externalities
Whether an economic agent’s decision creates an externality often depends on the institutional context in which the decision was made. Indeed, in orthodox economics, a technological or exogenous externality occurs just in case one agent’s economic welfare or production possibilities are directly affected by the market decisions of other agents. A pecuniary externality occurs just in case one consumer’s economic welfare or producer’s profit is affected indirectly by price changes caused by changes in other agents’ decisions. Similarly, an institutional or endogenous externality may arise whenever allocations are determined by a mechanism that is not strategy proof for some agent. Then even a resource balance constraint creates an institutional externality except in special cases such as when no individual agent’s action can affect market clearing prices — i.e., there are no pecuniary externalities
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