Logic operations in principle have been demonstrated based on the planar high-Tc Superconducting QUantum Interference Device (SQUID). Two kinds of logic gates were produced by using the focused ion beam (FIB) superconducting weak links fabricated in NdBa2Cu3O7-δ (NBCO) thin films. Logic gates investigated in this paper are (1) an rf-SQUID based logic gate which utilizes threshold characteristics, and (2) a dc-SQUID based logic gate which is an elementary gate of RSFQ circuits. Elementary logic operation such as (1) AND/OR logic and (2) SET-RESET flip-flop operation were successfully obtained in the logic gates. In addition to the present experimental results, some problems and future prospects are also discussed.

Recent progress of highly sensitive magnetmeter utilizing high Tc dc superconducting quantum interference device (SQUID) is reviewed briefly. Performance parameters of the SQUID magnetometer, such as field resolution, dynamic response and usability in unshielded environment, are focused on. Relationship between these performance parameters and SQUID characteristics are discussed quantitatively, and key factors which dominate each performance are clarified. With this result, design principle to obtain high performance SQUID magnetometer operating at T77K is shown. Present status on the performance of the magnetometer is discussed by comparing experimental results with theoretical predictions. Issues to much improve the performance of the high Tc SQUID magnetometer are also discussed.