An inductively coupled memory cell for NDRO with two Josephson junctions

A memory cell with a write junction in a horizontal stripline loop, and a sense junction controlled by the loop current, has been implemented for a minimum line width of 2 μm. The Josephson current density is about 10 kA cm$^{−2}$; the maximum number of flux quanta in the loop is about 100. The write junction is switched by coincident word and digit pulses; the latter being coupled inductively into a loop. The magnetic field of the digit pulse inside the write junction is zero so that resonances are avoided. After set-up of the initial current the cell is operated with pulses having much larger rise times than the current transfer time in the loop. The current transfer time deduced from measurements and simulations is below 100 ps.