429 research outputs found
Coulomb blockade thermometry using a two-dimensional array of tunnel junctions
We have measured current-voltage characteristics of two-dimensional arrays of
small tunnel junctions at temperatures from 1.5 K to 4.2 K. This corresponds to
thermal energies larger than the charging energy. We show that 2D-arrays can be
used as primary thermometers in the same way as 1D-arrays, and even have some
advantages over 1D-arrays. We have carried out Monte Carlo simulations, which
agree with our experimental results.Comment: 4 pages, 4 eps figures. Also available from Journal of Applied
Physics (http://link.aip.org/link/?jap/86/3844
Nonclassical microwave radiation from the dynamical Casimir effect
We investigate quantum correlations in microwave radiation produced by the
dynamical Casimir effect in a superconducting waveguide terminated and
modulated by a superconducting quantum interference device. We apply
nonclassicality tests and evaluate the entanglement for the predicted field
states. For realistic circuit parameters, including thermal background noise,
the results indicate that the produced radiation can be strictly nonclassical
and can have a measurable amount of intermode entanglement. If measured
experimentally, these nonclassicalilty indicators could give further evidence
of the quantum nature of the dynamical Casimir radiation in these circuits.Comment: 5 pages, 3 figure
Gain Dependence of the Noise in the Single Electron Transistor
An extensive investigation of low frequency noise in single electron
transistors as a function of gain is presented. Comparing the output noise with
gain for a large number of bias points, it is found that the noise is dominated
by external charge noise. For low gains we find an additional noise
contribution which is compared to a model including resistance fluctuations. We
conclude that this excess noise is not only due to resistance fluctuations. For
one sample, we find a record low minimum charge noise of qn = 9*10^-6
e/sqrt(Hz) in the superconducting state and qn = 9*10^-6 e/sqrt(Hz) in the
normal state at a frequency of 4.4 kHz.Comment: 10 pages, LaTex 2.09, 4 figures (epsfig
Scattering of coherent states on a single artificial atom
In this work we theoretically analyze a circuit QED design where propagating
quantum microwaves interact with a single artificial atom, a single Cooper pair
box. In particular, we derive a master equation in the so-called transmon
regime, including coherent drives. Inspired by recent experiments, we then
apply the master equation to describe the dynamics in both a two-level and a
three-level approximation of the atom. In the two-level case, we also discuss
how to measure photon antibunching in the reflected field and how it is
affected by finite temperature and finite detection bandwidth.Comment: 18 pages, 7 figure
Characterization of a Differential Radio-Frequency Single-Electron Transistor
We have fabricated and characterized a new type of electrometer that couples
two parallel single-electron transistors (SETs) to a radio-frequency tank
circuit for use as a differential RF-SET. We demonstrate operation of this
device in summing, differential, and single-SET operation modes, and use it to
measure a Coulomb staircase from a differential single Cooper-pair box. In
differential mode, the device is sensitive to uncorrelated input signals while
screening out correlated ones.Comment: 3 pages, 3 figures, submitted to Applied Physics Letter
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