Superconducting Quantum Electronics

With the surprising discovery of superconductivity at temperatures above 100 K, this field was not only brought into the public eye, but also stimulated research in universities, scientific institutions and industry, thus continuing the fascinating development which began with the discovery of the Josephson effect in the sixties. Cryoelectronics has become a special branch of cryophysics and cryotechnics and today plays a prominent role whenever high resolution and precision measurements are required. Motivated by this development, seven years ago scientists working in cryoelectronics in the Federal Republic of Germany felt the necessity for regular meetings allowing a free exchange of ideas and results achieved. Seminars under the title of "Kryoelektronische Bauelemente" were held for the first time at the Physikalisch-Technische Bundesanstalt in Braunschweig in 1982 on the occasion of the 100th anniversary of the birth of Walther MeiBner, a pioneer in superconductivity. Since then, meetings have been held every year at different venues in Germany. It is now felt that the status of this field necessitates a review of the results of the past, a description of the current state of the art, and a discussion of future perspectives. This book, entitled SUPERCONDUCTING QUANTUM ELECTRONICS is a collection of invited lectures and contributions which will inform the reader on the most interesting problems involving fundamentals, sensitive detectors and precision metrology being studied by different groups.

I Fundamentals.- Classical Dynamics of Josephson Tunnelling and Its Quantum Limitations.- 1. Introduction.- 2. Basic Properties of Josephson Junctions.- 2.1 The DC and the AC Josephson Effect.- 2.2 Circuit Implications.- 2.3 Damping Equivalent.- 3. Classical Dynamics of the Quantum Phase Shift in Pair- and Quasiparticle Tunnel Junctions.- 3.1 Quantum Phase Self-Coupling.- 3.2 Tunnel Junction Admittance.- 3.3 Special Cases.- 4. Macroscopic Quantum Phenomena Based on Josephson Tunnel Dynamics.- 4.1 Macroscopic Quantum Tunnelling.- 4.2 Quantum Charge Oscillations.- 4.2.1 Bloch Oscillations.- 4.2.2 Single-Electron Tunnelling (SET).- Modelling of Resistive Networks for Dispersive Tunnel Processes.- 1. Introduction.- 2. Classification of Different Essential Processes.- 3. The Macroscopic Dynamical Structure of Superconductive Tunnel Diodes.- 4. The Mapping of the Dynamical Structure on Technical Equivalent Systems.- 4.1 Mechanical Analogies.- 4.2 Electrical Equivalent Circuits.- 4.2.1 Circuit Model with Infinite Degree of Freedom.- 4.2.2 Circuit Model with Finite Degree of Freedom.- 5. Conclusion and Outlook.- Electromagnetic Properties of Superconductors Exact Solution of the Mattis-Bardeen Equations for Bulk Material and Thin Films.- 1. Introduction.- 2. Bulk Superconductors.- 2.1 Theories of the Normal and Anomalous Skin Effect.- 2.2 Solution of the Mattis-Bardeen Kernel K(q).- 2.3 Extreme Anomalous Skin Effect.- 2.4 Surface Impedance.- 3. Applications to Bulk Superconductors.- 3.1 Other Calculations.- 3.2 Microwave Region.- 3.3 Far Infrared Region.- 4. Thin Films.- 4.1 Theoretical Treatment.- 4.2 Complex Conductivity.- 5. Applications to Thin Films.- 5.1 Transition to Bulk Superconductors.- 5.2 Transmission Spectra.- 6. Conclusion.- II Sensitive Detectors.- High-Tc Josephson Contacts and Devices.- 1. Introduction.- 2. Technological Aspects.- 2.1 Thin Film Preparation.- 2.2 Microstructuring Procedures.- 3. Tunnel Contacts.- 4. Microbridges.- 4.1 Theoretical Model.- 4.2 Experimental Results.- 5. High-Tc SQUIDs.- 5.1 Single Layer Nb3Ge-DC-SQUIDs.- 5.2 Nb3Ge Multi-Layer Technique.- 5.3 Nb3Ge Multi-Layer DC-SQUID.- 6. High Frequency Applications.- 6.1 Microwave Driven Switching Device.- 6.2 Nanobridges as Relaxation Oscillators.- 6.3 FM-Read-Out Scheme for DC-SQUIDs.- 7. Emerging Developments: SQUIDs at 77 Kelvin.- Biomagnetic Sensors.- 1. Introduction.- 2. The Biomagnetic Method.- 3. Current Dipole Model.- 4. Detection Coil Configurations.- 4.1 Wire-Wound Flux Transformers.- 4.2 Thin Film Flux Transformers.- 4.3 Multisensor Configurations.- 5. Sensor Periphery.- 5.1 Dewars.- 5.2 Shielded Rooms.- 6. Possible Implementation of High-Tc Superconductors in Biomagnetic Instrumentation.- 7. Conclusion.- Josephson Junction as a Spectral Detector.- 1. Introduction.- 2. Current and Voltage Sensitivity.- 2.1 Autonomous Junction.- 2.2 Impressed RF Current.- 2.3 Oscillation Linewidth.- 2.4 External Circuit.- 3. Noise Equivalent Power.- 4. Spectrometer with Wide Frequency Span.- 4.1 Theory.- 4.2 Experiments.- 5. Outlook.- Superconducting Tunnel Junctions for Radioastronomical Receivers.- 1. Millimeter and Submillimeter Radiation from the Interstellar Medium.- 2. Description of Receivers for Radio Astronomy.- 2.1 Direct Detectors.- 2.2 Heterodyne Detection.- 3. The Quasiparticle and the Josephson Current in SIS Tunnel Junction.- 4. Fabrication and Properties of SIS and SIN Junctions.- 4.1 Lead Alloy Junctions.- 4.2 Refractory Metal Junctions.- 5. Quasiparticle Direct Detectors.- 5.1 Responsivity and Noise Equivalent Power.- 5.2 Frequency Limitation.- 5.3 Possible Gain Mechanism.- 6. Classical Mixing with the Schottky Diode.- 7. Quantum Mixing with the SIS Junction.- 7.1 Theoretical and Experimental Results of Quasipartide Mixing.- 7.2 Realization of Quasipartide Heterodyne Receivers for Radioastronomical Observations.- 7.3 Upper Frequency Limit.- 8. Mixing with SIN Junctions.- 9. Outlook for Quasiparticle Tunnel Junctions of the High-Tc Superconductor.- Low-Temperature Scanning Electron Microscopy of Superconducting Thin Films and Tunnel Junctions.- 1. Introduction.- 2. Electron Beam as a Local Heat Source.- 3. Spatial Structure in Superconducting Thin Films.- 4. Inhomogeneous Quasiparticle Tunneling.- 5. Inhomogeneous Pair Tunneling.- 6. Vortex States and Trapped Flux Quanta in Tunnel Junctions.- 7. Cryoelectronic Circuits and Tunnel Junction Arrays.- 8. Applications to Thin Films of High-Tc-Super conductors.- III Precision Metrology.- Josephson Series Array Potentiometer.- 1. Introduction.- 2. Circuit Design.- 3. Fabrication of the Circuits.- 4. Measuring System and Precision of the Standard Instrument.- 5. Design of an Integrated Potentiometer.- 6. The Use of High Critical Temperature Superconductors.- Cryogenic Current Comparator Metrology.- 1. Introduction.- 2. Theory and Operation of Cryogenic Current Comparators.- 2.1 Basic Principle.- 2.2 Practical Realizations of Cryogenic Current Comparators.- 2.3 Ratio Error of a Cryogenic Current Comparator.- 2.4 Optimization of the Signal-To-Noise Ratio.- 3. Resistance Ratio Measurements.- 3.1 Basic Principle.- 3.2 Practical Realizations.- 3.2.1 Deflection Method.- 3.2.2 Balance Method.- 3.3 Measurement of Quantized Hall Resistances and Establishment of a Resistance Scale.- 4. Future Developments.- Fast SQUID Pseudo Random Generators.- 1. Introduction.- 2. Principles of the Generation of Digital Random Noise.- 2.1 The Continuous Process of Generation.- 2.2 The Discrete Process of Generation.- 2.3 Pseudo-Random Noise.- 2.4 Synthetic Noise Sources for RF Frequencies.- 3. Superconducting Shift Registers for the Generation of Random Noise.- 3.1 Dynamics of a Single Josephson Element.- 3.2 Switching Performance of a SQUID.- 3.3 The Flux Shuttle.- 3.4 The Feedback Logic.- 3.5 Realization of a fast SQUID Shift Register.- 3.6 Modifications Using High Tc Superconductors.