'Momentum Computing' Pushes Technology's Thermodynamic Limits

Tue, 29 Mar 2022 05:00:00 GMT
Scientific American - Technology

Overheating is a major problem for today’s computers, but those of tomorrow might stay cool by...

"The conventional wisdom for a long time has been that the energy dissipation in reversible computing is proportional to speed," says computer scientist Michael Frank of Sandia National Laboratories in Albuquerque, N.M. To the Limit-And Beyond.

Silicon-based computing does not get near the Landauer limit anyway: currently such computing produces around a few thousands of Landauers in heat per logical operation, and it is hard to see how even some superefficient silicon chip of the future could get below 100 or so.

The two researchers and their co-workers introduced the basic idea of momentum computing last year.

"We're being parasites on the quantum computing community!" Crutchfield merrily admits.

Ray and Crutchfield performed simulations that suggest that, under certain conditions, JJ circuits should be able to support their momentum computing approach.

Momentum computing is closely analogous to a reversible-computing concept called ballistic computing that was proposed in the 1980s: in it, information is encoded in objects or particles that move freely through the circuits under their own inertia, carrying with them some signal that is used repeatedly to enact many logical operations.

Whereas, in ballistic computing, a particle's velocity simply transports it through the device, allowing the particle to ferry information from input to output, Crutchfield says, in momentum computing, a particle's velocity and position collectively allow it to embody a unique and unambiguous sequence of states during a computation.

Ray and Crutchfield "Have probably done the most thorough job so far of demonstrating this at the level of the theory and simulation of individual devices." Even so, Frank warns that all the various approaches for ballistic and momentum computing "Are still a long way from becoming a practical technology."

Ultimately, he anticipates consumer-grade momentum computing could realize energy-efficiency gains of 1,000-fold or more over current approaches.

"Momentum computing will lead to a conceptual shift in how we see information processing in the world," he says-including how information is processed in biological systems.