The Josephson Effect: The Original SQUIDs

Arnold H. Silver presents a first-hand account of three pioneering experiments, imbedding two Josephson tunnel junctions in thin film multiply connected superconducting circuits, illustrated: Two-junction interference superimposed on single junction Fraunhofer diffraction. The Aharonov-Bohm effect of a vector potential in a magnetic field-free region, Kinetic inductance in thin superconducting films via superconducting pair de-Broglie waves.

The first experiments demonstrating macroscopic quantum interference in superconductors were performed in 1962 and 1963 at the Ford Motor Company Scientific Laboratory as the analog of two-slit interference.

 These experiments followed some unusual microwave observations in superconductors and the demonstrations of flux quantization in superconductors and the Josephson junction. Following these experiments, our efforts shifted to bulk niobium structures using "point-contact" junctions as prototype Josephson junctions, resulting in the invention of the dc (two-junction) and rf (one-junction) Superconducting Quantum Interference Devices, which we named SQUIDs. I will present a first-hand account of the unique sequence of events that led to these discoveries and inventions.