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The IEEE 14th International Superconductive Electronics Conference (ISEC 2013) was held in Cambridge, Massachusetts, USA from July 7 to 11, 2013. The ISEC is a biennial conference focused entirely on superconductive electronics. The first ISEC occurred in 1987 in Tokyo, Japan. It was followed by meetings in Tokyo (1989), Glasgow (UK, 1991), Boulder (USA, 1993), Nagoya (Japan, 1995), Berlin (Germany,...
As part of a joint Stanford/IBM effort to build a scanning SQUID microscopy user facility at Stanford, we have designed and fabricated three types of scanning SQUID microscope sensors. The first is a SQUID susceptometer, with a symmetric, gradiometric design, pickup loops with 0.1 micrometer minimum feature size integrated into the SQUID body through coaxially shielded leads, integrated flux modulation...
The recent implementation of three-dimensional microwave cavities coupled to superconducting transmon qubits has led to dramatic improvements in qubit coherence times [1]. Besides the superconducting aluminum cavities that have been used in many such measurements, other recent experiments have utilized copper cavities [2] with coherence times now approaching 0.1 ms. We are investigating the effects...
We have designed and tested energy-efficient single flux quantum (eSFQ) circuits for use in practical circuits. The first circuit is a 184-bit shift register for acquisition memory to store short transient events. The second circuit is a 16-bit deserializer integrated with an analog-to-digital converter modulator. The deserializer converts a high speed oversampling delta modulator 1-bit data stream...
We develop an energy efficient digital data link connecting cryogenic superconducting single flux quantum (SFQ) circuits to room-temperature electronics. The design is based on low-temperature (4 K) superconductor ERSFQ SFQ/dc drivers, high-temperature superconductor data cables spanning 4 K to 70 K temperature stages, mid-temperature (70 K) polarization modulation vertical cavity surface emitting...
A method has been developped to take into account the presence of a local external magnetic field in Superconducting Quantum Interference Devices (SQUIDs) loops composing Rapid Single-Flux-Quantum (RSFQ) circuits, through modifications of circuit inductances. A good agreement is observed between analytical formulas and simulations performed by time-domain softwares. The agreement with the first experiments...
We are developing a large-scale reconfigurable data-path (LSRDP) based on single-flux-quantum (SFQ) circuits to establish a fundamental technology for future high-performance computing systems. In the LSRDP, an SFQ floating-point adder (FPA) is one of the main and most complicated circuit blocks. In our previous study, we implemented an SFQ half-precision (16-bit) bit-serial FPA using the ISTEC 2...
A superconducting digital-RF receiver with high ingest-rate data recording capability has been developed. The data recorder unit uses standard PC components with state-of-the-art solid-state drives and interfaces with the superconductor analog-to-digital converter (ADC) through a commercial FPGA board. High-speed data ingest rates exceeding 3.2 GBps have been demonstrated successfully with single-bit...
Optical refrigeration is a solid-state cooling technology that has already achieved working temperatures of 114 K and is expected to cool below 80 K in the near future. This approach to cooling generates no vibrations and is immune to magnetic or electromagnetic interference. Furthermore, the coolers can be much lighter and more compact than mechanical coolers. At the minimum temperatures, the heat...
Being frequency tunable sources, Josephson junctions are attractive for the generation of high frequency electromagnetic radiation. Recently, coherent off-chip THz radiation with an extrapolated output power of some μW was observed. Different mechanisms, like geometry resonance and heating effect, have been raised to explain how the junctions in the stack are synchronized, while there is no consensus...
If Josephson and spintronic technologies can be successfully integrated to produce a cryogenic memory that can be controlled with single-flux quantum pulses, then they may enable ultra-low-power, high-speed computing. We have developed hybrid Josephson junctions with Nb electrodes, using barrier materials composed of both pseudo-spin valves (PSV) and magnetic-clusters. Our choice of relatively weak...
We studied multi-quantum beam detectors using a superconducting tunnel junction (STJ) array with neutron absorbers. Using a neutron absorber for each of the STJs, we expected the STJ detector to exhibit a high spatial resolution and high detection efficiency for neutrons as well as radiative beams such as X-rays. To obtain diffraction patterns of the X-ray and neutrons, we propose the use of a multi-quantum...
We propose a method of measuring quantum superposition states of a single spin with a superconducting resonator. Following the von Neumann's postulate of the reduction, it seems that we cannot obtain more information about the superposition states other than the eigenvalue by a single observation. However, the indirect quantum measurement has the possibility to measure the ratio of components of the...
We have evaluated the electrical characteristics of NbN/Al-AlNx/NbN tunnel junctions fabricated on sapphire-C or fused-silica substrates. NbN/Al-AlNx/NbN multilayers were prepared by reactive dc-magnetron sputtering deposition of lower and upper NbN layers, and rf-magnetron sputtering deposition of the Al layer, followed by radical-nitridation. The junctions showed low sub-gap leakage currents in...
Modeling the magnetic field generated by currents in thin-film superconducting structures is useful to a broad range of applications. Present methods calculate the magnetic field around such structures from two-dimensional current sheets. We present an efficient and accurate algorithm to calculate the magnetic field at arbitrary locations in three dimensions, both internal and external to the structures...
Flux trapping in superconducting devices has shown to be detrimental to the consistent operation of superconducting electronics (SCE). Approaches to improve reliability of SCE components have focused on introduction of flux trap regions and highly elaborate degaussing procedures. Nevertheless, a controlled and reproducible method to assure the elimination of trapped flux on SCE devices remains elusive...
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