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The dominating noise mechanism in mesoscopic samples at low
temperatures is shot noise. In some cases, it is the limiting factor for the
measurement sensitivity, but shot noise itself may be the actual quantity of
interest as it, contrary to the thermal noise, contains information about
the sample, complement to that of the average current.
Many of the interesting predictions for noise have been obtained for
nonlinear elements (with voltage-dependent response) whose resistance is
typically in the range of kOhms or more. However, measurement of shot
noise in such samples is not always straightforward as the excess noise
added by the amplifiers depends on the sample impedance, and thus on the
applied voltage. |
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We are presently interested in shot noise
experiments as well as measurements of the third moment of current
fluctuations in a variety of mesoscopic systems.
To access these these quantities in samples with large impedance requires
matching circuits and extra measures in order to preserve the information
within the accessible band width.
In addition, we are working on the noise optimization of read-out
electronics for qubits. One candidate for fast
read-out purposes is the RF-SET, an amplitude modulated single electron
transistor (SET) that is the fastest and the most sensitive
electrometer known
today. |
