183 research outputs found
Superconducting Quantum Interference Device Amplifiers with over 27 GHz of Gain-Bandwidth Product Operated in the 4 GHz--8 GHz Frequency Range
We describe the performance of amplifiers in the 4 GHz--8 GHz range using
Direct Current Superconducting Quantum Interference Devices(DC SQUIDs) in a
lumped element configuration. We have used external impedance transformers to
couple power into and out of the DC SQUIDs. By choosing appropriate values for
coupling capacitors, resonator lengths and output component values, we have
demonstrated useful gains in several frequency ranges with different
bandwidths, showing over 27 GHz of power gain-bandwidth product. In this work,
we describe our design for the 4 GHz--8 GHz range and present data
demonstrating gain, bandwidth, dynamic range, and drift characteristics.Comment: four pages, 5 figure
Input Impedance and Gain of a Gigahertz Amplifier Using a DC SQUID in a Quarter Wave Resonator
Due to their superior noise performance, SQUIDs are an attractive alternative
to high electron mobility transistors for constructing ultra-low-noise
microwave amplifiers for cryogenic use. We describe the use of a lumped element
SQUID inductively coupled to a quarter wave resonator. The resonator acts as an
impedance transformer and also makes it possible for the first time to
accurately measure the input impedance and intrinsic microwave characteristics
of the SQUID. We present a model for input impedance and gain, compare it to
the measured scattering parameters, and describe how to use the model for the
systematic design of low-noise microwave amplifiers with a wide range of
performance characteristics
Measurement of non-Gaussian shot noise: influence of the environment
We present the first measurements of the third moment of the voltage
fluctuations in a conductor. This technique can provide new and complementary
information on the electronic transport in conducting systems. The measurement
was performed on non-superconducting tunnel junctions as a function of voltage
bias, for various temperatures and bandwidths up to 1GHz. The data demonstrate
the significant effect of the electromagnetic environment of the sample.Comment: 13 pages, for the SPIE International Symposium on Fluctuations and
Noise, Maspalomas, Gran Canaria, Spain (May 2004
Dispersive Photon Blockade in a Superconducting Circuit
Mediated photon-photon interactions are realized in a superconducting
coplanar waveguide cavity coupled to a superconducting charge qubit. These
non-resonant interactions blockade the transmission of photons through the
cavity. This so-called dispersive photon blockade is characterized by measuring
the total transmitted power while varying the energy spectrum of the photons
incident on the cavity. A staircase with four distinct steps is observed and
can be understood in an analogy with electron transport and the Coulomb
blockade in quantum dots. This work differs from previous efforts in that the
cavity-qubit excitations retain a photonic nature rather than a hybridization
of qubit and photon and provides the needed tolerance to disorder for future
condensed matter experiments.Comment: 4 pages, 3 figure
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