1,652 research outputs found
Theory of the Bloch Oscillating Transistor
The Bloch oscillating transistor (BOT) is a device, where single electron
current through a normal tunnel junction can be used to enhance Cooper pair
current in a mesoscopic Josephson junction leading to signal amplification. In
this paper we develop a theory, where the BOT dynamics is described as a
two-level system. The theory is used to predict current-voltage characteristics
and small-signal response. Transition from stable operation into hysteretic
regime is studied. By identifying the two-level switching noise as the main
source of fluctuations, the expressions for equivalent noise sources and the
noise temperature are derived. The validity of the model is tested by comparing
the results with simulations.Comment: 11 pages, 8 figure
Control of Coulomb blockade in a mesoscopic Josephson junction using single electron tunneling
We study a circuit where a mesoscopic Josephson junction (JJ) is embedded in
an environment consisting of a large bias resistor and a normal metal -
superconductor tunnel junction (NIS). The effective Coulomb blockade of the JJ
can be controlled by the tunneling current through the NIS junction leading to
transistor-like characteristics. We show using phase correlation theory and
numerical simulations that substantial current gain with low current noise
( fA/) and noise temperature (
0.1 K) can be achieved. Good agreement between our numerical simulations and
experimental results is obtained.Comment: 5 pages, 4 figures, RevTE
Description of self-synchronization effects in distributed Josephson junction arrays using harmonic analysis and power balance
Power generation and synchronisation in Josephson junction arrays have
attracted attention for a long time. This stems from fundamental interest in
nonlinear coupled systems as well as from potential in practical applications.
In this paper we study the case of an array of junctions coupled to a
distributed transmission line either driven by an external microwave or in a
self-oscillating mode. We simplify the theoretical treatment in terms of
harmonic analysis and power balance. We apply the model to explain the large
operation margins of SNS- and SINIS-junction arrays. We show the validity of
the approach by comparing with experiments and simulations with
self-oscillating es-SIS junction arrays.Comment: 5 pages, 3 figure
Differential Bloch Oscillating Transistor Pair
We examine a Bloch Oscillating Transistor pair as a differential stage for
cryogenic low-noise measurements. Using two oppositely biased, nearly symmetric
Bloch Oscillating Transistors, we measured the sum and difference signals in
the current gain and transconductance modes while changing the common mode
signal, either voltage or current. From the common mode rejection ratio we find
values dB even under non-optimal conditions. We also characterize the
noise properties and obtain excellent noise performance for measurements having
source impedances in the M range.Comment: 8 pages, 3 figure
RSFQ devices with selective dissipation for quantum information processing
We study the possibility to use frequency dependent damping in RSFQ circuits
as means to reduce dissipation and consequent decoherence in RSFQ/qubit
circuits. We show that stable RSFQ operation can be achieved by shunting the
Josephson junctions with an circuit instead of a plain resistor. We derive
criteria for the stability of such an arrangement, and discuss the effect on
decoherence and the optimisation issues. We also design a simple flux generator
aimed at manipulating flux qubits
Dynamics of Bloch oscillating transistor near the bifurcation threshold
The tendency to bifurcate can often be utilized to improve performance characteristics of amplifiers or even to build detectors. The Bloch oscillating transistor is such a device. Here, we show that bistable behavior can be approached by tuning the base current and that the critical value depends on the Josephson coupling energy EJ of the device. We demonstrate current-gain enhancement for the device operating near the bifurcation point at small EJ. From our results for the current gains at various EJ, we determine the bifurcation threshold on the EJ-base current plane. The bifurcation threshold curve can be understood using the interplay of interband and intraband tunneling events.Peer reviewe
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