Abstract: A lanthanum aluminate (LaAlO.sub.3) substrate on which thin films of layered perovskite copper oxide superconductors are formed. Lanthanum aluminate, with a pseudo-cubic perovskite crystal structure, has a crystal structure and lattice constant that closely match the crystal structures and lattice constants of the layered perovskite superconductors. Therefore, it promotes epitaxial film growth of the superconductors, with the crystals being oriented in the proper direction for good superconductive electrical properties, such as a high critical current density. In addition, LaAlO.sub.3 has good high frequency properties, such as a low loss tangent and low dielectric constant at superconductive temperatures. Finally, lanthanum aluminate does not significantly interact with the superconductors. Lanthanum aluminate can also used to form thin insulating films between the superconductor layers, which allows for the fabrication of a wide variety of superconductor circuit elements.

Abstract: A lanthanum aluminate ( LaAlO.sub.3) substrate on which thin films of layered perovskite copper oxide superconductors are formed. Lanthanum aluminate, with a pseudo-cubic perovskite crystal structure, has a crystal structure and lattice constant that closely match the crystal structures and lattice constants of the layered perovskite superconductors. Therefore, it promotes epitaxial film growth of the superconductors, with the crystals being oriented in the proper direction for good superconductive electrical properties, such as a high critical current density. In addition, LaAlO.sub.3 has good high frequency properties, such as a low loss tangent and low dielectric constant at superconductive temperatures. Finally, lanthanum aluminate does not significantly interact with the superconductors. Lanthanum aluminate can also used to form thin insulating films between the superconductor layers, which allows for the fabrication of a wide variety of superconductor circuit elements.

Abstract: A Josephson junction voltage standard based on rf controlled dc SQUID's is proposed. A microwave signal is injected using rf control lines. A D/A converter based on series-connected rf controlled SQUID's is described.

Abstract: A superconducting bidirectional counter. The device finds application in very fast and very high precision analog-to-digital (A/D) converters. The counter does not need to consume any bias power.

Abstract: A periodic superconducting device signal quantizer for the fine resolution of the magnetic flux quantum .PHI..sub.0 =2*10.sup.-15 Wb realized by a phase wheel 20 or a phase tree 100. The signal quantizer is used in conjunction with a superconducting A/D converter for achieving the 8-11 bit A/D converters with gigahertz, multi-gigahertz bandwidth. A method for an extra-bit resolution of the analog signal using the signal quantizer is described.

Abstract: A superconducting infrared photodetector employing SQUID (Superconducting Quantum Interference Device) measurement of fluxon flow in thin superconducting granular films to provide sensitive, low-noise detection of infrared radiation. The superconducting infrared photodetector includes a plurality of superconducting detector elements connected in parallel or series, means for supplying a bias current to the detector elements, and a digital or analog SQUID readout circuit. Each detector element includes a thin granular film of superconducting material which forms a randomly connected array of weakly coupled superconductors. The weakly coupled superconductors promote the formation of oppositely-polarized fluxons, which are driven to opposite sides of the film when subjected to the bias current. Incident radiation causes an increase in this fluxon flow, generating a voltage change.

Abstract: A superconducting analog-to digital converter comprises an input line, a soliton generator, a phase sampler, and a decoder. The soliton generator includes a nonlinear transmission line and a gradient current source. The transmission line is a series of inductive links separated from a superconducting ground plane by Josephson junction. The gradient current source induces gradient pump currents that are inductively coupled into the transmission line. The gradient establishes a three-cycle soliton. A time-varying current input signal is inductively coupled to the transmission line so that the local pump current changes as a function of changes in the input signal. These changes cause the soliton to move, and thus change its phase, along the transmission line. Sixty-four comparators of the phase sampler track the phase of the soliton. The digital readout of the phase sampler is then decoded to determine the value of the signal input.

Abstract: A track and hold circuit for use with an analog signal quantizer, comprising a multiple of four superconductor-insulator-superconductor (SIS) junctions arranged in a bridge. A storage inductance is connected to opposite nodes of the bridge, with an analog signal input being orthogonally injected into the bridge. The SIS junctions are magnetically suppressed from reaching a superconducting, zero-voltage state, limiting switching of the SIS junctions between a subgap voltage, high differential resistive behavior and a low differential resistive behavior exhibited when a gap voltage is attained. Preferably, each SIS junction includes a magnet that suppresses the superconductivity. Alternatively, a control wire may be used to provide a magnetic field to suppress superconductivity.

Abstract: The present invention is directed to systems and methods capable of analyzing a wide variety of input signal waveforms to arbitrate their arrival sequence with a high resolution. In an exemplary embodiment, the apparatus is an arbiter circuit which includes an input means for inputting signals whose waveforms are to be analyzed, a comparator means for distinguishing arrival times of the input signals, the comparator means further including means for quantizing flux, and an output means for outputting information which identifies the arrival of at least one of the input signals. In an alternate embodiment, feedback means are provided for compensating asymmetries in the comparator means.

Abstract: A magnetometer having high sensitivity and high resolution is achieved using superconductive circuit elements. The magnetometer includes a pick-up coil, amplifying transformer quantum flux parametron (QFP), latch, feedback gate and feedback inductor fabricated with superconducting elements and coupled to a bidirectional counter. The magnetometer implements an on-chip negative feedback loop. The pick-up coil senses an external magnetic field or gradient resulting in an induced current which is amplified and fed to the QFP which generates a directional indicator signal sent to the latch. When the polarity of the indicator is indicated as corresponding to the polarity of a latch clock signal, a current signal is sent to the feedback gate causing a packet of quantum flux to be generated. The packet is fed back through the feedback inductor, inducing a current in the pick-up coil which opposes the induced current attributable to the external magnetic field.

Abstract: A high-performance superconducting analog-to-digital (A/D) converter providing high-speed, high-resolution A/D conversion with low power consumption. The superconducting A/D converter of the present invention includes a bidirectional binary counter having n stages of triple-junction reversible flip-flops, where n is the number of bits of the digital output, and a pair of superconducting inductors for inductively coupling an analog input current to the bidirectional counter. The bidirectional counter algebraically counts incremental changes in the analog input current, increasing the binary count for positive incremental changes in the analog current and decreasing the binary count for negative incremental changes in the analog current. The bidirectional counter requires no gate bias, thus requiring minimal power for operation.

Abstract: A high-speed, high-resolution superconducting counting A/D converter providing greatly increased conversion speeds with a low device count. The superconducting counting A/D converter includes a double-junction SQUID quantizer and a bidirectional binary counter having n stages of grounded four-junction SQUID flip-flops, where n is the number of bits of accuracy of the counter. The quantizer continuously tracks an analog signal, generating up-count and down-count voltage pulses of the same polarity on two different output lines for increasing and decreasing values of the analog current, respectively. The bidirectional binary counter algebraically counts the voltage pulses, increasing the binary count when up-count pulses are received and decreasing the binary count when downcount pulses are received.

Abstract: A high-speed, high-resolution superconducting counting A/D converter providing greatly increased conversion speeds with a low device count. The superconducting counting A/D converter includes includes a double-junction SQUID quantizer and a bidirectional binary counter having n stages of floating four-junction SQUID flip-flops, where n is the number of bits of accuracy of the counter. The quantizer continuously tracks an analog signal, generating up-count and down-count voltage pulses of the same polarity on two different output lines for increasing and decreasing values of the analog current, respectively. The bidirectional binary counter algebraically counts the voltage pulses, increasing the binary count when up-count pulses are received and decreasing the binary count when down-count pulses are received. Several techniques for reading the contents of the bidirectional binary counter at the end of each sampling interval are also disclosed.

Abstract: An apparatus for determining and displaying selected characteristics of a film formed on the surface of a glass ribbon includes a scanning head mounted on a track for movement above the filmed surface of the glass ribbon. The scanning head has a source of light pulses generated from a tungsten lamp and chopper, filtered to simulate daylight and focused on the filmed surface. An integrating sphere is also mounted on the scanning head and has an entrance port formed in a wall thereof for collecting a portion of the light being reflected from the surface. Optically filtered detectors mounted in detector ports formed in the wall of the sphere generate output signals representing the "Y" and "Z" components of the collected light on the CIE X,Y,Z, tristimulus scale.