Among the many candidates for storing quantum bits, or qubits, are electrons, atoms, molecules and quantum dots. However, over the last few years, researchers have been focusing on storing quantum bits in silicon as a promising avenue towards realizing a quantum computer. Now, researchers from the University of Surrey, University College London, Heriot-Watt University in Edinburgh, the Radboud University in Nijmegen, and ETH Zürich/EPF Lausanne/Paul Scherrer Institute in Switzerland have reported the ability to control the quantum state of qubits embedded in silicon and readout the result by a simple electrical measurement. A paper describing their findings appears in the 20 March edition of Nature Communications

The qubits are phosphorus atoms trapped inside the silicon layer. Because the spin state of the outer electron of these atoms can remain in a state of superposition of the two possible spin states, these qubits are therefore called “orbital qubits.” They can retain a superposition state for a fraction of a millisecond before they are disrupted. The researchers demonstrated that they could switch the quantum state of the phosphorus atoms with laser pulses in about a picosecond (10-12 s), which is a thousand times faster than achieved with previous similar experiments. The advantage of these short pulses is that in future computers, operations could be performed easier on qubits that retain their quantum state for a very short time, says Ben Murdin, a physicist at the University of Surrey and corresponding author of the paper.

The researchers also reported that they could determine the quantum state of a qubit by measuring the amount of current passing through the silicon. The point of the experiment, says Murdin, is to show that it’s possible to use completely standard commercial silicon, and a simple voltmeter for the readout of quantum superpositions. "It's the first electrical detection of orbital qubits in silicon,” he says. And the only piece of fancy equipment that’s required is the laser.

Murdin notes that electrical readouts of quantum states have advantages for other quantum technologies too. "I don't know how to make a quantum computer, but this method would help enormously if you want an atomic clock or a quantum magnetometer,” the Surrey professor says.

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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
Vertical
Mountains and cresting waves made of cartoon cats and large green coins.
Frank Stockton
Pink

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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