We observed the recently predicted quantum suppression of dynamical Coulomb blockade on short coherent conductors by measuring the conductance of a quantum point contact embedded in a tunable on-chip circuit. Taking advantage of the circuit modularity we measured most parameters used by the theory. This allowed us to perform a reliable and quantitative experimental test of the theory. Dynamical...

The breakdown of conductance quantization in a quantum point contact in the presence of random long-range impurity potential is discussed. It is shown that in the linear response regime a decisive role is played by the indirect backscattering mechanism via quasilocalized states at the Fermi level; this can provide much higher backscattering rate than any direct backscattering process. For the r...

We develop a simple analytical model to study the influence of different material systems on the operation of a quantum-point-contact spin filter. Such a device has been predicted to allow for local control of the spin polarization in a semiconductor, and for direct electrical detection of the induced spin polarization. Narrow band-gap semiconductors, such as InAs and InSb, are predicted to exh...

We present a detailed analysis of finite-frequency noise for the ν = 5/2 fractional quantum Hall state in a quantum point contact geometry. The results were obtained within the Pfaffian and anti-Pfaffian models. We show that the behaviour of the coloured noise allows us to unambiguously discriminate among tunnelling excitations with different charges. Optimal values of the external bias are fou...

Spectral density of current fluctuations in a short ballistic superconducting quantum point contact is calculated for arbitrary bias voltages V. Contrary to a common opinion that the supercurrent flow in Josephson junctions is coherent process with no fluctuations, we find extremely large current noise that is caused by the supercurrent coherence. An unusual feature of the noise, besides its ma...

Scanning a charged tip above the two-dimensional electron gas inside a gallium arsenide/aluminum gallium arsenide nanostructure allows the coherent electron flow from the lowest quantized modes of a quantum point contact at liquid helium temperatures to be imaged. As the width of the quantum point contact is increased, its electrical conductance increases in quantized steps of 2 e(2)/h, where e...