Low-temperature superconductors have been developed, with an eye on high-performance computing, since the 1960s. But the technology languished, pursued by only a handful of research departments, as funding proved hard to come by. Now signs of technological maturity and the emergence of potentially lucrative applications suggest that that low-temperature superconducting is turning a corner.

The rapidly expanding wireless market provides an ideal target for an electronics capability that can hook an antenna to an A/D converter and digitally emulate virtually any RF component in real-time. That capability has caught the eye of the military, which is enlisting Hypres in a bid to reduce the Defense Department's entire spectrum of military communications systems to a single, superconducting software radio.

"We have been doing a lot of work under SBIR [Small Business Innovation Research] grants and government projects such as the JTRS [Joint Tactical Radio Systems] program," said Hypres CEO Jack Rosa. "It's a dual-use program, so they expect commercial products to be developed as well, something that we certainly favor."

The company developed a line of high-performance oscilloscopes in the late 1980s as its first foray into commercial products. Hypres has been selling products into such niche areas as superconducting quantum interference device magnetometers, for reading brain waves, and standard-volt chips, used in labs and by government standards organizations.

"We developed a standard for the volt with NIST [National Institute of Standards and Technology]. Superconducting devices can define the volt more accurately than any other method," said Rosa. The development has turned into a good business for Hypres, particularly since the breakup of the Soviet Union, as the former member states have been developing their own, independent standards.

Hypres' IC technology encodes binary bits in the form of individual magnetic flux quanta to form a class of digital logic circuits known as rapid single-flux quantum (RSFQ) logic. The technique was invented by Konstantine Likharev and two colleagues at the University of Moscow in the early 1980s, just as IBM Corp. was shutting down its Josephson junction research effort. A leading IBM researcher, Sadeg Faris, left IBM to found Hypres and soon recruited Likharev, now the company's chief of operations.

Likharev also set up an RSFQ lab at the State University of New York at Stony Brook. That facility is staffed by several researchers from his earlier project at the University of Moscow.

RSFQ has been the key breakthrough for building stable logic circuits based on superconducting niobium wires that conduct electricity without resistance at a temperature of around 5 K. Before the advent of RSFQ, superconducting electronics schemes tried to imitate the voltage-level methods used in semiconductor electronics. But that approach was not able to take much advantage of the lack of electrical resistance in superconducting wires.

State-of-the-art RSFQ circuits are in the 100- to 1,000-gate density range and run comfortably at 20 GHz with very little power dissipation-and that's at 3-micron design rules. Mixed-signal devices can reach 100 GHz easily, and the speed record in laboratory experiments is 750 GHz.