Josephson analog to digital converter for low-level signals

Abstract

This is a superconducting analog-to-digital converter for producing a digital output signal which is a function of an analog input signal. The analog-to-digital converter uses a nonhysteresis-shunted Josephson junction, an input superconducting inductor, and an output Josephson junction, connected in superconducting loop relationship. A flux proportional to an analog input signal is coupled into the input inductor and a constant bias current source connected such that the current divides between the nonhysteresis-shunted Josephson junction and the output Josephson junction with the bias current source providing a current of at least about the sum of the critical currents of said Josephson junctions to provide voltage pulses across the nonhysteresis-shunted Josephson junction even with a constant level of flux. A Josephson junction integrating counter circuit is connected to sense the ac portion of voltage across the output Josephson junction and the Josephson junction integrating counter circuit is gated. The number of oscillations in the voltage across the output Josephson junction in a predetermined period of time is a function of the analog input signal and the count of the Josephson junction integrating counter circuit during the predetermined period provides a digital output which is a function of to the input signal.

Dependencies are inferred from the claim text.