We produced a double-layer thin-film heater to detrap magnetic flux in a SQUID sensor. The heater is integrated on a sensor chip, and consists of a lower resistor layer and an upper superconducting layer to cancel the magnetic field produced by the heater current. The SQUID sensor is cooled below its critical temperature with a temperature gradient to detrap the flux completely. To make the gradient, we had to decrease heater power to zero over an interval exceeding 10-4 second in our experiment, which is almost equal to the sensor chip's thermal time constant. The integrated heater effectively controls the temperature profile and detraps flux in the sensor.

Josephson integrated circuit technology has progressed remarkably since niobium junctions were introduced in 1983. At present, it is feasible to make LSI level circuits, such as a few thousand gate microprocessor and a few kilobit memory. It has been demonstrated that these circuits are operated with much faster speed and lower power consumption than semiconductor circuits. This paper describes the performance of these circuits.

We report the results of experiments on a Josephson RAM having an access time of 590 ps and a power dissipation of 19 mW. To design such high-speed memory, we developed new gates and circuits and used high-speed techniques. This paper details the design of the 4K bit Josephson RAM.