Chip-Scale Atomic Clock

The ultimate in precision--the cesium clock--has been miniaturized

4 min read

The standard by which clocks in the United States are set is a cesium-based atomic clock in Boulder, Colo., that loses less than a nanosecond per day. It’s the size of a small car and draws roughly a kilowatt of power. Less-accurate commercial atomic clocks, which keep time by watching the vibrations of atoms, are typically the size of a suitcase, though not nearly as portable as one. But now, for the first time, atomic clock accuracy is available in a form small enough and power-efficient enough for backpack-size battery-powered devices. Someday an atomic clock might even fit into a smartphone.

Earlier this year, Symmetricom, of San Jose, Calif., introduced the first commercial chip-scale atomic clock, the SA.45s. It measures 4 by 3.5 by 1.1 centimeters, weighs 35 grams, and draws a paltry 115 milliwatts. The tiny clock is accurate to within about less than half a microsecond per day.

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Two Startups Are Bringing Fiber to the Processor

Avicena’s blue microLEDs are the dark horse in a race with Ayar Labs’ laser-based system

5 min read
Diffuse blue light shines from a patterned surface through a ring. A blue cable leads away from it.

Avicena’s microLED chiplets could one day link all the CPUs in a computer cluster together.

Avicena

If a CPU in Seoul sends a byte of data to a processor in Prague, the information covers most of the distance as light, zipping along with no resistance. But put both those processors on the same motherboard, and they’ll need to communicate over energy-sapping copper, which slow the communication speeds possible within computers. Two Silicon Valley startups, Avicena and Ayar Labs, are doing something about that longstanding limit. If they succeed in their attempts to finally bring optical fiber all the way to the processor, it might not just accelerate computing—it might also remake it.

Both companies are developing fiber-connected chiplets, small chips meant to share a high-bandwidth connection with CPUs and other data-hungry silicon in a shared package. They are each ramping up production in 2023, though it may be a couple of years before we see a computer on the market with either product.

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