We analyze the frequency-dependent current fluctuations induced into a gate
near a quantum point contact or a quantum chaotic cavity. We use a current and
charge conserving, effective scattering approach in which interactions are
treated in random phase approximation. The current fluctuations measured at a
nearby gate, coupled capacitively to the conductor, are determined by the
screened charge fluctuations of the conductor. Both the equilibrium and the
non-equilibrium current noise at the gate can be expressed with the help of
resistances which are related to the charge dynamics on the conductor. We
evaluate these resistances for a point contact and determine their
distributions for an ensemble of chaotic cavities. For a quantum point contact
these resistances exhibit pronounced oscillations with the opening of new
channels. For a chaotic cavity coupled to one channel point contacts the charge
relaxation resistance shows a broad distribution between 1/4 and 1/2 of a
resistance quantum. The non-equilibrium resistance exhibits a broad
distribution between zero and 1/4 of a resistance quantum.Comment: 9 pages, two-column Revtex, 6 figures include
