Quasi-one junction SQUIDs as comparators for analog-to-digital conversion

Comparators based on single junction superconducting quantum interference devices (SQUIDs) have been fabricated and tested. These comparators demonstrate the periodic behavior of multiple junction SQUIDs without the disturbances due to flux mode boundary crossings, promising higher speed. The proper functioning of all components of a full analog-to-digital converter, including the quasi-one-junction-SQUID (QOJS) and the sampling circuit to measure its output, is demonstrated. The only problem observed is that the magnitude of the pulse in the Josephson sampler is too small to measure the full output of the QOJS. This has recently been corrected. Simulations indicate that 4 b of resolution at 10 GHz input bandwidth, or higher resolution at lower bandwidths, should be achievable.