381 research outputs found
Josephson tunnel junction controlled by quasiparticle injection
A Josephson tunnel junction transistor based on quasiparticle injection is
proposed. Its operation relies on the manipulation of the electron distribution
in one of the junction electrodes. This is accomplished by injecting
quasiparticle current through the junction electrode by two additional tunnel
coupled superconductors. Both large supercurrent enhancement and fast quenching
can be achieved with respect to equilibrium by varying quasiparticle injection
for proper temperature regimes and suitable superconductor combinations. Joined
with large power gain this makes the device attractive for applications where
reduced noise and low power dissipation are required.Comment: 4 pages, 3 figure
Geometric Landau-Zener interferometry in a superconducting charge pump
We propose a new type of interferometry, based on geometric phases
accumulated by a periodically driven two-level system undergoing multiple
Landau-Zener transitions. As a specific example, we study its implementation in
a superconducting charge pump. We find that interference patterns appear as a
function of the pumping frequency and the phase bias, and clearly manifest
themselves in the pumped charge. We also show that the effects described should
persist in the presence of realistic decoherence.Comment: 5 pages, 3 figure
Statistics of heat exchange between two resistors
We study energy flow between two resistors coupled by an arbitrary linear and
lossless electric circuit. We show that the fluctuations of energy transferred
between the resistors are determined by random scattering of photons on an
effective barrier with frequency dependent transmission probability
. We express the latter in terms of the circuit parameters. Our
results are valid in both quantum and classical regimes and for non-equilibrium
electron distribution functions in the resistors.Comment: 7 pages, 4 figures. Published version. New figures added, discussion
extende
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
Geometry of an adiabatic passage at a level crossing
We discuss adiabatic quantum phenomena at a level crossing. Given a path in
the parameter space which passes through a degeneracy point, we find a
criterion which determines whether the adiabaticity condition can be satisfied.
For paths that can be traversed adiabatically we also derive a differential
equation which specifies the time dependence of the system parameters, for
which transitions between distinct energy levels can be neglected. We also
generalize the well-known geometric connections to the case of adiabatic paths
containing arbitrarily many level-crossing points and degenerate levels.Comment: 7 pages, 6 figures, RevTeX4, changes requested by Phys. Rev.
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