Margins of a 16-ps/bit interferometer shift register

Static and dynamic properties of an interferometer with five equal Josephson junctions are investigated as a single-flux quanta shift-register model. A flux quantum is stored in any loop without a bias current or magnetic field. A flux quantum is shifted from one interferometer loop to the adjacent one by applying a magnetic-field control pulse only to one in terferometer loop at a time. Shift current margins determined statically and dynamically are larger than about ±30 percent; the write current margins are ±25 percent. Within these tolerances, and for a maximum Josephson current density of 10 kA/ cm², delays of 16 ps/bit, including shift and write, have been simulated.