3,985 research outputs found
Time-Resolved Detection of Individual Electrons in a Quantum Dot
We present measurements on a quantum dot and a nearby, capacitively coupled,
quantum point contact used as a charge detector. With the dot being weakly
coupled to only a single reservoir, the transfer of individual electrons onto
and off the dot can be observed in real time in the current signal from the
quantum point contact. From these time-dependent traces, the quantum mechanical
coupling between dot and reservoir can be extracted quantitatively. A similar
analysis allows the determination of the occupation probability of the dot
states.Comment: 3 pages, 3 figure
Finite bias charge detection in a quantum dot
We present finite bias measurements on a quantum dot coupled capacitively to
a quantum point contact used as a charge detector. The transconductance signal
measured in the quantum point contact at finite dot bias shows structure which
allows us to determine the time-averaged charge on the dot in the non-blockaded
regime and to estimate the coupling of the dot to the leads.Comment: 6 pages, 4 figure
Thermally excited Trivelpiece–Gould modes as a pure electron plasma temperature diagnostic
Thermally excited plasma modes are observed in trapped, near-thermal-equilibrium pure electron plasmas over a temperature range of 0.05<kT<5 eV. The modes are excited and damped by thermal fluctuations in both the plasma and the receiver electronics. The thermal emission spectra together with a plasma-antenna coupling coefficient calibration uniquely determine the plasma (and load) temperature. This calibration is obtained from the mode spectra themselves when the receiver-generated noise absorption is measurable; or from separate wave reflection/absorption measurements; or from kinetic theory. This nondestructive temperature diagnostic agrees well with standard diagnostics, and may be useful for expensive species such as antimatter
Thermally excited fluctuations as a pure electron plasma temperature diagnostic
Thermally excited charge fluctuations in pure electron plasma columns provide a diagnostic for the plasma temperature over a range of 0.05 0.2, so that Landau damping is dominant and well modeled by theory. The third method compares the total (frequency-integrated) number delta N of fluctuating image charges on the wall antenna to a simple thermodynamic calculation. This method works when lambda(D)/R-p > 0.2
Frequency-selective single photon detection using a double quantum dot
We use a double quantum dot as a frequency-tunable on-chip microwave detector
to investigate the radiation from electron shot-noise in a near-by quantum
point contact. The device is realized by monitoring the inelastic tunneling of
electrons between the quantum dots due to photon absorption. The frequency of
the absorbed radiation is set by the energy separation between the dots, which
is easily tuned with gate voltages. Using time-resolved charge detection
techniques, we can directly relate the detection of a tunneling electron to the
absorption of a single photon
Imaging a Coupled Quantum Dot - Quantum Point Contact System
We performed measurements on a quantum dot and a capacitively coupled quantum
point contact by using the sharp metallic tip of a low-temperature scanning
force microscope as a scanned gate. The quantum point contact served as a
detector for charges on the dot or nearby. It allowed us to distinguish single
electron charging events in several charge traps from charging events on the
dot. We analyzed the tip-induced potential quantitatively and found its shape
to be independent of the voltage applied to the tip within a certain range of
parameters. We estimate that the trap density is below 0.1% of the doping
density and that the interaction energy between the quantum dot and a trap is a
significant portion of the dot's charging energy. Possibly, such charge traps
are the reason for frequently observed parametric charge rearrangements.Comment: 6 pages, 5 figure
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