Pi-phase shift josephson structures

One of the unique aspects of superconductivity is the phase coherence of the macroscopic wavefunction. It provides the basis for most concepts of superconducting electronic devices, such as SQUIDs and RSFQ circuitry. The phase coherence also underlies the principle of fluxoid quantization in superconducting ring structures. In recent years, an interest has arisen in introducing phase-shifting elements in superconducting circuits. Here, I will describe various techniques to implement such a phase shift, outline the potential interest for device applications and will attempt to provide an outlook for future developments in this field. Rather than providing an extensive review for a general readership, this paper aims to briefly introduce various aspects of phase-shift devices to experts in the field of Josephson electronics and to list the most important recent experimental developments in this field.