545 research outputs found
Optical Probe of Quantum Shot Noise Reduction at a Single-Atom Contact
Visible and infra-red light emitted at a Ag-Ag(111) junction has been
investigated from tunneling to single atom contact conditions with a scanning
tunneling microscope. The light intensity varies in a highly nonlinear fashion
with the conductance of the junction and exhibits a minimum at conductances
close to the conductance quantum. The data are interpreted in terms of current
noise at optical frequencies, which is characteristic of partially open
transport channels
Entanglement in a Noninteracting Mesoscopic Structure
We study the time dependent electron-electron and electron-hole correlations
in a mesoscopic device which is splitting an incident current of free fermions
into two spatially separated particle streams. We analyze the appearance of
entanglement as manifested in a Bell inequality test and discuss its origin in
terms of local spin-singlet correlations already present in the initial channel
and the action of post-selection during the Bell type measurement. The time
window over which the Bell inequality is violated is determined in the
tunneling limit and for the general situation with arbitrary transparencies. We
compare our results with alternative Bell inequality tests based on coincidence
probabilities.Comment: 9 pages, 2 figure
Superconductor-metal transition in an ultrasmall Josephson junction biased by a noisy voltage source
Shot noise in a voltage source changes the character of the quantum
(dissipative) phase transition in an ultrasmall Josephson junction: The
superconductor-insulator transition transforms into the superconductor-metal
transition. In the metallic phase the IV curve probes the voltage distribution
generated by shot noise, whereas in the superconducting phase it probes the
counting statistics of electrons traversing the noise junction.Comment: 4 pages, 3 figures. Corrected typos and style, added reference
A Josephson junction as a detector of Poissonian charge injection
We propose a scheme of measuring the non-Gaussian character of noise by a
hysteretic Josephson junction in the macroscopic quantum tunnelling (MQT)
regime. We model the detector as an (under)damped resonator. It transforms
Poissonian charge injection into current through the detector, which samples
the injection statistics over a floating time window of length , where is the quality factor of the resonator and its resonance frequency. This scheme ought to reveal the Poisson character
of charge injection in a detector with realistic parameters
Effect of the shot-noise on a Coulomb blockaded single Josephson junction
We have investigated how the Coulomb blockade of a mesoscopic Josephson
junction in a high-impedance environment is suppressed by shot noise from an
adjacent junction. The presented theoretical analysis is an extension of the
phase correlation theory for the case of a non-Gaussian noise. Asymmetry of the
non-Gaussian noise should result in the shift of the conductance minimum from
zero voltage and the ratchet effect (nonzero current at zero voltage), which
have been experimentally observed. The analysis demonstrates that a Coulomb
blockaded tunnel junction in a high impedance environment can be used as an
effective noise detector.Comment: 4 pages, 1 figure; figure and typos corrected, added reference
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