A device that turns light into sound has allowed researchers to capture lightning in a bottle, in a sense, slowing down the light beams enough so that they can be easily stored and manipulated.

Researchers at the University of Sydney in Australia, have figured out how to turn a light wave into a sound wave, creating an acoustic memory that they say will help data centers save energy by eliminating some electrical connections between processors. They reported their work in a recent issue of Nature Communications.

“Our vision is to replace the electronic interconnects between different processors and computing machines with photonic ‘wires,’’’ said Birgit Stiller, a postdoctoral researcher who led the project. “So light transmission will be used instead of electronic connections.”

The team built a chip that consists of a spiral-shaped waveguide made from a soft glass called chalcogenide, sandwiched between two stiffer pieces of silica glass. As a light beam travels through the chip, it is met by another pulse of light that has a slightly different frequency. The difference between the frequencies of the two light beams is a “beat,” a wave with a frequency 100,000 times lower, thus turning the light wave into a sound wave.

The sound wave lives for a brief time—several nanoseconds—in the spiral chalcogenide waveguide. To read it out, the device reverses the process, adding the beat frequency to a light pulse to recreate the original light wave.

In standard optical fibers, light waves are prevented from leaking out of the fiber by a difference in refractive index between the core of the fiber and the cladding wrapped around it. In a similar way, the two types of glass keep the sound wave in place; the speed of sound is much slower in the chalcogenide than in the silica.

Slowing down the waves provides time to synchronize different signals coming from different processors. That eliminates the need to convert the optical signal to an electronic signal. Electronics can produce excess heat and require more energy, which are important issues in the big data centers owned by Google, Amazon, or Microsoft, Stiller says.

Further work with the design and materials might allow the sound waves to be stored longer, although the memory already lasts long enough for the use they envision. She and her team hope to refine the work further, with an eye to building a prototype of a manufacturable chip within the next few years.

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The Spectacular Collapse of CryptoKitties, the First Big Blockchain Game

A cautionary tale of NFTs, Ethereum, and cryptocurrency security

8 min read
Mountains and cresting waves made of cartoon cats and large green coins.
Frank Stockton

On 4 September 2018, someone known only as Rabono bought an angry cartoon cat named Dragon for 600 ether—an amount of Ethereum cryptocurrency worth about US $170,000 at the time, or $745,000 at the cryptocurrency’s value in July 2022.

It was by far the highest transaction yet for a nonfungible token (NFT), the then-new concept of a unique digital asset. And it was a headline-grabbing opportunity for CryptoKitties, the world’s first blockchain gaming hit. But the sky-high transaction obscured a more difficult truth: CryptoKitties was dying, and it had been for some time.

The launch of CryptoKitties drove up the value of Ether and the number of transactions on its blockchain. Even as the game's transaction volume plummeted, the number of Ethereum transactions continued to rise, possibly because of the arrival of multiple copycat NFT games.

That perhaps unrealistic wish becomes impossible once the downward spiral begins. Players, feeling no other attachment to the game than growing an investment, quickly flee and don’t return.

Whereas some blockchain games have seemingly ignored the perils of CryptoKitties’ quick growth and long decline, others have learned from the strain it placed on the Ethereum network. Most blockchain games now use a sidechain, a blockchain that exists independently but connects to another, more prominent “parent” blockchain. The chains are connected by a bridge that facilitates the transfer of tokens between each chain. This prevents a rise in fees on the primary blockchain, as all game activity occurs on the sidechain.

Yet even this new strategy comes with problems, because sidechains are proving to be less secure than the parent blockchain. An attack on Ronin, the sidechain used by Axie Infinity, let the hackers get away with the equivalent of $600 million. Polygon, another sidechain often used by blockchain games, had to patch an exploit that put $850 million at risk and pay a bug bounty of $2 million to the hacker who spotted the issue. Players who own NFTs on a sidechain are now warily eyeing its security.

Remember Dragon

The cryptocurrency wallet that owns the near million dollar kitten Dragon now holds barely 30 dollars’ worth of ether and hasn’t traded in NFTs for years. Wallets are anonymous, so it’s possible the person behind the wallet moved on to another. Still, it’s hard not to see the wallet’s inactivity as a sign that, for Rabono, the fun didn’t last.

Whether blockchain games and NFTs shoot to the moon or fall to zero, Bladon remains proud of what CryptoKitties accomplished and hopeful it nudged the blockchain industry in a more approachable direction.

“Before CryptoKitties, if you were to say ‘blockchain,’ everyone would have assumed you’re talking about cryptocurrency,” says Bladon. “What I’m proudest of is that it was something genuinely novel. There was real technical innovation, and seemingly, a real culture impact.”

This article was corrected on 11 August 2022 to give the correct date of Bryce Bladon's departure from Dapper Labs.

This article appears in the September 2022 print issue as “The Spectacular Collapse of CryptoKitties.”

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