1,054 research outputs found
Bloch inductance in small-capacitance Josephson junctions
We show that the electrical impedance of a small-capacitance Josephson
junction includes besides the capacitive term also an inductive
term . Similar to the known Bloch capacitance , the Bloch
inductance also depends periodically on the quasicharge , and its
maximum value achieved at always exceeds the value of
the Josephson inductance of this junction at fixed . The
effect of the Bloch inductance on the dynamics of a single junction and a
one-dimensional array is described.Comment: 5 pages incl. 3 fig
Assessing T cell clonal size distribution: a non-parametric approach
Clonal structure of the human peripheral T-cell repertoire is shaped by a
number of homeostatic mechanisms, including antigen presentation, cytokine and
cell regulation. Its accurate tuning leads to a remarkable ability to combat
pathogens in all their variety, while systemic failures may lead to severe
consequences like autoimmune diseases. Here we develop and make use of a
non-parametric statistical approach to assess T cell clonal size distributions
from recent next generation sequencing data. For 41 healthy individuals and a
patient with ankylosing spondylitis, who undergone treatment, we invariably
find power law scaling over several decades and for the first time calculate
quantitatively meaningful values of decay exponent. It has proved to be much
the same among healthy donors, significantly different for an autoimmune
patient before the therapy, and converging towards a typical value afterwards.
We discuss implications of the findings for theoretical understanding and
mathematical modeling of adaptive immunity.Comment: 13 pages, 3 figures, 2 table
Josephson tunnel junctions with nonlinear damping for RSFQ-qubit circuit applications
We demonstrate that shunting of Superconductor-Insulator-Superconductor
Josephson junctions by Superconductor-Insulator-Normal metal (S-I-N) structures
having pronounced non-linear I-V characteristics can remarkably modify the
Josephson dynamics. In the regime of Josephson generation the phase behaves as
an overdamped coordinate, while in the superconducting state the damping and
current noise are strikingly small, that is vitally important for application
of such junctions for readout and control of Josephson qubits. Superconducting
Nb/AlO/Nb junction shunted by Nb/AlO/AuPd junction of S-I-N type
was fabricated and, in agreement with our model, exhibited non-hysteretic I-V
characteristics at temperatures down to at least 1.4 K.Comment: 4 pages incl. 3 figure
Josephson charge-phase qubit with radio frequency readout: coupling and decoherence
The charge-phase Josephson qubit based on a superconducting single charge
transistor inserted in a low-inductance superconducting loop is considered. The
loop is inductively coupled to a radio-frequency driven tank circuit enabling
the readout of the qubit states by measuring the effective Josephson inductance
of the transistor. The effect of qubit dephasing and relaxation due to electric
and magnetic control lines as well as the measuring system is evaluated.
Recommendations for operation of the qubit in magic points producing minimum
decoherence are given.Comment: 11 pages incl. 6 fig
Dynamics of Josephson junctions and single-flux-quantum networks with superconductor-insulator-normal metal junction shunts
Within the framework of the microscopic model of tunneling, we modelled the
behavior of the Josephson junction shunted by the
Superconductor-Insulator-Normal metal (SIN) tunnel junction. We found that the
electromagnetic impedance of the SIN junction yields both the
frequency-dependent damping and dynamic reactance which leads to an increase in
the effective capacitance of the circuit. We calculated the dc I-V curves and
transient characteristics of these circuits and explained their quantitative
differences to the curves obtained within the resistively shunted junction
model. The correct operation of the basic single-flux-quanta circuits with such
SIN-shunted junctions, i.e. the Josephson transmission line and the toggle
flip-flop, have also been modelled.Comment: 8 pages incl. 7 figure
Radio-frequency Bloch-transistor electrometer
A quantum-limited electrometer based on charge modulation of the Josephson
supercurrent in the Bloch transistor inserted into a superconducting ring is
proposed. As this ring is inductive coupled to a high-Q resonance tank circuit,
the variations of the charge on the transistor island (input signal) are
converted into variations of amplitude and phase of radio-frequency
oscillations in the tank. These variations are amplified and then detected. The
output noise, the back-action fluctuations and their cross-correlation are
computed. It is shown that our device enables measurements of the charge with a
sensitivity which is determined by the energy resolution of its amplifier, that
can be reduced down to the standard quantum limit of \hbar/2. On the basis of
this setup a "back-action-evading" scheme of the charge measurements is
proposed.Comment: 5 pages incl. 2 figure
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