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IEEE Transactions on Magnetics

A Josephson junction time domain reflectometer with room temperature access

Stephen R. Whiteley, Gert K. G. Hohenwarter, S. M. Faris

Published Mar 1, 1987• 22 citations
Publisher

Abstract

Using a novel chip architecture and cooling method, a superconducting Josephson Junction time domain reflectometer subsystem has been developed which provides wide bandwidth access to the room temperature environment. Presented is an overview of the subsystem, with emphasis on the cryogenic circuitry employed. Results and performance limitations are described.

DOI
10.1109/tmag.1987.1064882

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Using a novel chip architecture and cooling method, a superconducting Josephson Junction time domain reflectometer subsystem has been developed which provides wide bandwidth access to the room temperature environment. Presented is an overview of the subsystem, with emphasis on the cryogenic circuitry employed. Results and performance limitations are described.
HYPRES, Inc. has introduced to the commercial marketplace a Sampling Oscilloscope/Time Domain Reflectometer (TDR) based on Josephson junction technology. The unit offers measurement performance commensurate with the inherent high speed of the Josephson elements, e.g., bandwidths in excess of 70 GHz and rise times on the order of 5 ps. A Josephson {rigger recognizer and delay circuit allows triggering of the sampling oscilloscope from the signal itself, with full view of the trigger point. Input modules offering different sensitivities or TDR capability are quickly interchangeable, and operating temperature is achieved in less than one minute. The technical details of the cooling technique and the chip circuitry will be described in this paper .
HYPRES, Inc. has introduced a Sampling Oscilloscope/Time Domain Reflectometer (TDR) based on Josephson junction technology to the commercial marketplace. The unit offers measurement performance commensurate with the inherent high speed of the Josephson elements, e.g., risetimes on the order of 8 ps. The Josephson circuitry is contained on a single 1.1 × 1.6 fused silica substrate and housed in an interchangeable measurement module. Only the portion of the chip which contains the superconducting circuitry is cooled with a coplanar transmission line providing the wide bandwidth interface between the room temperature and cryogenic environments less than 1cm apart.
Niobium nitride has a superconducting transition temperature nearly twice that of niobium. A 5-ps time-domain reflectometer chip based on NbN technology has been designed, fabricated, and tested. The circuit is operable up to 9 K. The NbN process and limitations are discussed, and present drawbacks in the junction fabrication method are pointed out. Electrical properties are discussed, the circuit operation is described, and simulations are presented that are based on model parameters extracted from device measurements. The actual output of the circuit is presented as evidence of basic functionality. This is the first demonstration of a functional high-speed circuit based entirely on a compound superconductor technology and operable at temperatures above 8 K.>
The promises of the ultrahigh-performance properties of superconductivity and Josephson junction technologies have been known for quite some time. This presentation describes the first superconducting electronics and measurement system and its important role as a major tool to advance microwave and millimeter wave technologies. This breakthrough tool is a sampling oscilloscope with 5-ps rise time, 50-μV sensitivity, and a time domain reflectometer with 8-ps rise time. In order to achieve these performance goals, several technological hurdles had to be overcome including perfecting a manufacturing process for building Josephson junction IC chips, developing an innovative cooling technique, developing interfaces and interconnections with bandwidths in excess of 70 GHz, and developing the room-temperature hardware and software necessary to make the instruments convenient, easy to use, easy to learn, in addition to making available functions and features users have come to expect from sophisticated digital test instrumentation. These technological developments are stepping stones leading to the realization of more sophisticated and complex electronic systems satisfying the needs of scientists, technologists, and engineers. The unprecedented speed and sensitivity make it possible to attack new frontiers.
Superconducting qubits based on Josephson junctions are one of the leading candidates for building a largescale quantum information processor. There have been significant advances in the performance of superconducting qubits over the past decade and there is currently rapid progress in the development of systems with up to tens of qubits. In order to build to yet larger systems, new techniques will need to be developed to address the overhead requirements for room-temperature electronics hardware and cryostat wiring for controlling and reading out large numbers of qubits. One approach to this challenge involves implementing more of the qubit control and readout in the low-temperature environment. I will describe our efforts on integrating superconducting classical digital circuitry with superconducting qubits for coherent control and readout.
Abstract Providing radio frequency (RF) signals to cryogenic circuits requires bulky and expensive cabling interfacing specialized RF electronics at room temperature. Superconducting-normal metal-superconducting Josephson junction arrays (JJAs) can change this paradigm by placing the RF source and detector on-chip. In this work, we demonstrate that DC-biased JJAs can emit signals in the C-band frequency spectrum and beyond, with a minimal linewidth of 106.5 ± 0.1 MHz and maximum power of 11.9 fW. We fabricate JJAs comprised of amorphous MoGe or NbTiN superconducting islands and metallic Au weak links. Temperature, magnetic field, applied current, and device design are explored to control the RF sources, while we identify important features that affect the ideal source behavior. Combined with the ability of these JJAs to detect microwave radiation, these sources allow us to propose a fully DC-operated cryogenic on-chip measurement platform that is an alternative to the high-frequency circuitry currently required for quantum applications.