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An important property of shot noise is that it is typically proportional
to the average current. This property may be taken advantage of by using an
adiabatic cyclostationary drive that modulates the noise by a few
first harmonics of the base frequency.
We have analyzed theoretically a setup (see the figure on the right)
where a time-dependent current consisting of a DC bias and two sinusoidal
harmonics, is driven through a sample. The down-converted noise power
spectrum is found to vary depending on the local-oscillator phase of the
mixer. The theory of this phase-dependent noise suggests that the
cyclostationary drive can be used to improve the sensitivity of a
radio-frequency single electron transistor (RF-SET) by a small fraction.
In addition, we have shown that this scheme can be used to measure the
shot noise accurately even in nonlinear high-impedance samples.
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The
modulation setup . Current i(t) =I0 + I1 sin(\omega t) + I2 cos(2 \omega
t) + n(t) flows through the sample. Output current is y(t) = i(t) x D(t),
where D(t) = D0 sin(\omega t + \phi_0). When the sample exhibits
current-dependent shot noise, the down-converted noise power spectrum varies
depending on the local-oscillator phase of the mixer. |
