A superconducting neural circuit is fabricated for the first time by use of a niobium integrated-circuit technology. Fluxon pulses on Josephson transmission lines (JTLs) are used as neural impulses. In this circuit a threshold element (a neuron) is composed of two JTL elements connected through a resistor. The conductance value of the resistor represent a synaptic strength. The fan-in and the fan-out are accomplished by the biased JTL branches. The operation of 2-bit neural based A/D converter is successfully observed. These circuits do not require any hysteretic Josephson junctions, and hence, have a potential to be fabricated with the high-Tc superconductors.

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Two types of current doublers, which operate in a sub-nanoampere range, have been fabricated as prototypes of a precise current multiplier for metrological application. The current doubling function of the devices is based on the quantum currentmirror effect in coupled arrays of small Josephson junctions. Both types of devices comprise three arrays of small Josephson junctions: the first device has two serial short arrays coupled to one long array, and the second device has three arrays of the same size arranged in parallel. The arrays for the current input are the long array in the first device and one of the three arrays in the second device, and a parallel connection of the other two arrays in each device forms the output port. In both types of devices, a current fed to the input array is doubled in the output circuit, which includes the connected arrays, up to about 100 pA with the accuracy AE3 pA, which is the uncertainty of the measurement system, by correlated tunnelings of Cooperpair charge solitons in the arrays. The feasibility of producing a current multiplier has been ascertained on the basis of this effect.

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