A superconducting filter-type powering device (SFPD) for the Josephson computer system

To supply a large ac powering current to the low-impedance Josephson computer from the external source, some type of impedance-matching circuit is required. The SFPDs are band-pass filter type superconducting impedance transformers, designed to operate at around 0.5GHz with impedance transfer ratio as large as 16000. The SFPD can potentially be design to operate at much higher frequencies. Its resonant-mode operation results in high current gain and stable duty in the power network. The SFPD for a hypothetical 8K-gate Josephson computer system was designed and fabricated. The capacitors in the circuit consist of Nb electrodes and low-loss Nb2O5dielectrics. The inductors and the dummy resistors consist of Nb and Mo thin films respectively. For the 3-stage SFPD, the operation at 0.40∼0.53GHz was confirmed with the current gain of 95 and the VSWR of 5. The 3mΩ input impedance of the Josephson system was transferred to 27Ω.