Energy-efficient superconducting circuits could be key to future supercomputers - Transistor-based semiconductors have dominated the computing industry since its start. But a much more exotic, transistor-less option has long been lurking in the wings. Superconducting circuits, which boast resistance-less wires and ultrafast switches, can perform the tasks that silicon-based systems do in a fraction of the time.
Energy-efficient superconducting circuits could be key to future supercomputers - Transistor-based semiconductors have dominated the computing industry since its start. But a much more exotic, transistor-less option has long been lurking in the wings. Superconducting circuits, which boast resistance-less wires and ultrafast switches, can perform the tasks that silicon-based systems do in a fraction of the time.
Abstract. While human progress in the world of electronics, computers and computing is undeniable, new researches show that we can achieve greater speed and lower power consumption based on the principles of quantum physics. Changing from the digital world of today, which is based on CMOS transistors and the electric current, to quantum with no electric current and based on magnetic flux, is now in the middle of its way. Clearly any research in this area or even a comprehensive scientific attention is laudable from the experts’ viewpoint. This paper tries to show quantum computers more tangible by describing and analyzing some basic principles and explaining the entrance to this technology. In this article it is explained how the spintronics, superconductivity, and Josephson junction open the ways to the next generation of faster, more compact, and more energy-efficient computers in future; computers that bring about several hundred times the speed and negligible power consumption, along with the revolution of basic principles of electronics. We'll see how the spin transistors transfer data in lower speed and volume, using the electron spin direction to be high or low, or how the superconductivity, which is the key to the future supercomputers, solve the problem of supercomputers power consumption using technologies such as RSFQ.
The superconducting tunnel effect predicted by Brian Josephson in 1962 is looking increasingly promising for another very practical application—as logic and memory circuits for computers. Josephson-junction circuits are capable of high switching speeds (50–100 picosec have already been obtained). And because such circuits operate at voltages comparable to the superconducting energy gap, the heat generated is typically microwatts, thousands of times lower than high-speed transistor circuits. The diminished heat-removal problem allows one to pack the Josephson circuits much closer than semiconductor circuits. Once high switching speeds are achieved, this packability becomes extremely important because then the major limitation on computer speed is how fast the electrical signal takes to move from one circuit to another.
Special Section on Progress & Trend of Superconductor-based ComputersIt is our great pleasure to have a Special Section entitled "Progress & Trend of Superconductor-based Computers" in IEICE Transactions on Electronics.Superconducting devices based on Josephson junctions exhibit low power consumption and fast switching.Superconducting transmission lines are free of dispersion up to several hundred GHz.Unique logic circuits such as fast single flux quantum (SFQ) circuits and ultralow power adiabatic quantum-flux parametron (AQFP) logic circuits were proposed and have been improved.These circuits have been well developed based on not only their theoretical advantage but also reliable design and fabrication technology of superconducting integrated circuits.Recently, strong interest on quantum computing motivates the development of superconducting quantum-bits, control and readout circuits, and their integration.In this Special Section, seven invited papers and a contributed one describe these topics: two papers for SFQ, four for AQFP, and two for key devices for quantum circuits.Finally, I would like to appreciate activities of all authors, reviewers, and members in editorial committee for completing this special section.
Quantum computers are based on the theory of quantum mechanics, and their powerful parallel data processing capability is expected to solve many mathematical problems that too are difficult to be handled by classical computers. Especially with the increase of data processing volume, the quantum advantage is more obvious. Among the many physical systems for quantum computers, superconducting quantum circuit and semiconductor quantum dot computers show amazing potential due to their compatibility with traditional integrated circuit process technology and ultrashort gating time of nanoseconds. Superconducting qubits consisting of Josephson junctions and superconducting coplanar capacitors are easily integrated into a large scale for their simple circuit structure and conventional semiconductor process compatibility. Semiconductor qubits made from isotopically purified silicon (Si)-based materials greatly suppress nuclear spin noise, and decoherence times of ultralong milliseconds can be achieved. In this article, we systematically describe the challenges faced by superconducting qubits and semiconductor qubits in hot issues such as error correction and decoherence and look into the future development of superconducting quantum computers and Si-based semiconductor quantum computers.
Superconductive electronics offers a unique combination of high bandwidth and low power for mission critical hardware such as digital processors at 20 to 100 GHz, microwatt per bit analog to digital converters, large digital switches at multi-Gb/s data rates, and low noise parametric amplifiers. This cryogenic technology, typically operating at a few degrees or a few tens of degrees Kelvin, depends upon the unique physics of superconducting materials such as Nb, NbN, and YBaCuO, and the fundamental circuit element, the Josephson junction (JJ) to create unique architectures of unprecedented design efficiency and performance. These circuits are based on the single flux quantum (SFQ) logic family, a technology that has no parallel in semiconductor electronics. Digital data is transmitted by voltage pulses with amplitude less than 1 mV, but at extremely high speeds. Individual gates have been operated as high as 370 GHz. In this paper, we present a brief overview of superconductive digital technology, describe some recent circuits, and discuss how the challenges to superconductive technology are being met, including the use of multi-chip module (MCM) technology, and the potential use of III-V HBT and HEMT circuits to provide interface drivers and amplifiers, possibly operated cryogenically.
In the shadow of high-temperature superconductivity, 35 years of research in low-temperature superconductor ICs quietly comes to fruition, yielding the world's fastest circuits. They are made with a superconducting metal, niobium, rather than a compound semiconductor. Their exotic technology is based on Josephson junction devices and the transmission of single quanta of magnetic flux along superconductor interconnects. This paper describes these ICs and also a logic family called rapid single flux quantum (RSFQ) logic, which is based on the storage and transmission of quanta of magnetic flux.