Superconducting computing: Difference between revisions

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Superconducting computing research has been pursued by the U. S. [[National Security Agency]] since the mid-1950s. However, progress could not keep up with the [[Moore's law|increasing performance]] of standard CMOS technology. As of 2016 there are no commercial superconducting computers, although research and development continues.<ref name=":1">{{Cite web|url=https://spectrum.ieee.org/computing/hardware/will-the-nsa-finally-build-its-superconducting-spy-computer|title=Will the NSA Finally Build Its Superconducting Spy Computer?|last=Brock|first=David C.|date=2016-04-24|website=IEEE Spectrum|access-date=2016-04-21}}</ref>

Research in the mid-1950s to early 1960s focused on the [[cryotron]] invented by [[Dudley Allen Buck]], but the liquid-helium temperatures and the slow switching time between superconducting and resistive states caused this research to be abandoned. In 1962 [[Brian Josephson]] established the theory behind the [[Josephson effect]], and within a few years IBM had fabricated the first Josephson junction. IBM invested heavily in this technology from the mid-1960s to 1983. By the mid-1970s IBM had constructed a [[superconducting quantum interference device]] using these junctions, mainly working with [[lead]]-based junctions and later switching to lead/niobium junctions. In 1980 the Josephson computer revolution was announced by IBM through the cover page of the May issue of Scientific American. One of the reasons which justified such a large-scale investment lies in that Moore's law - enunciated in 1965 - was expected to slow down and reach a plateau 'soon'. However, on the one hand Moore's law kept its validity, while the costs of improving superconducting devices were basically borne entirely by IBM alone and the latter, however big, could not compete with the whole world of semiconductors which provided nearly limitless resources .<ref name="De Liso2020">N. De Liso, G. Filatrella, D. Gagliardi, C. Napoli (2020). [https://doi.org/10.1093/icc/dtz051 "Cold numbers: Superconducting supercomputers and presumptive anomaly"], Industrial and Corporate Change, vol. 29, no. 2, pp.485-505, 2020.</ref>. Thus, the program was shut down in 1983 because the technology was not considered competitive with standard semiconductor technology. The Japanese [[Ministry of International Trade and Industry]] funded a superconducting research effort from 1981 to 1989 that produced the [[ETL-JC1]], which was a 4-bit machine with 1,000 bits of RAM.<ref name=":1"/>

In 1983, [[Bell Labs]] created niobium/[[Aluminium oxide|aluminum oxide]] Josephson junctions that were more reliable and easier to fabricate. In 1985, the [[Rapid single flux quantum]] logic scheme, which had improved speed and energy efficiency, was developed by researchers at [[Moscow State University]]. These advances led to the United States' Hybrid Technology Multi-Threaded project, started in 1997, which sought to beat conventional semiconductors to the petaflop computing scale. The project was abandoned in 2000, however, and the first conventional petaflop computer was constructed in 2008. After 2000, attention turned to [[superconducting quantum computing]]. The 2011 introduction of [[reciprocal quantum logic]] by Quentin Herr of [[Northrop Grumman]], as well as energy-efficient rapid single flux quantum by Hypres, were seen as major advances.<ref name=":1"/>