Intel bets on silicon transistors as basis for quantum computing
Intel is refusing to follow the quantum crowd by backing ultra-pure silicon qubits for quantum computers, instead of superconductors. Intel said its silicon qubits represents data in a quantum property known as the "spin" of a single electron, which is trapped inside a modified version of existing transistors. The focus for two teams working in Oregon and the Netherlands is to make the best qubits and then, using Intel's experience, scale up production.

Intel has a team of quantum hardware engineers in Portland, Oregon, who collaborate with researchers in the Netherlands, at TU Delft’s QuTech quantum research institute, under a $50 million grant established last year. Earlier this month Intel’s group reported that they can now layer the ultra-pure silicon needed for a quantum computer onto the standard wafers used in chip factories.

This strategy makes Intel an outlier among industry and academic groups working on qubits, as the basic components needed for quantum computers are known. Other companies can run code on prototype chips with several qubits made from superconducting circuits (see “Google’s Quantum Dream Machine”). No one has yet advanced silicon qubits that far.

A quantum computer would need to have thousands or millions of qubits to be broadly useful, though. And Jim Clarke, who leads Intel’s project as director of quantum hardware, argues that silicon qubits are more likely to get to that point (although Intel is also doing some research on superconducting qubits). One thing in silicon’s favor, he says: the expertise and equipment used to make conventional chips with billions of identical transistors should allow work on perfecting and scaling up silicon qubits to progress quickly.

Intel’s silicon qubits represent data in a quantum property called the “spin” of a single electron trapped inside a modified version of the transistors in its existing commercial chips. “The hope is that if we make the best transistors, then with a few material and design changes we can make the best qubits,” says Clarke.

Another reason to work on silicon qubits is that they should be more reliable than the superconducting equivalents. Still, all qubits are error prone because they work on data using very weak quantum effects (see “Google Researchers Make Quantum Components More Reliable”).

The new process that helps Intel experiment with silicon qubits on standard chip wafers, developed with the materials companies Urenco and Air Liquide, should help speed up its research, says Andrew Dzurak, who works on silicon qubits at the University of New South Wales in Australia. “To get to hundreds of thousands of qubits, we will need incredible engineering reliability, and that is the hallmark of the semiconductor industry,” he says.

Companies developing superconducting qubits also make them using existing chip fabrication methods. But the resulting devices are larger than transistors, and there is no template for how to manufacture and package them up in large numbers, says Dzurak.

Chad Rigetti, founder and CEO of Rigetti Computing, a startup working on superconducting qubits similar to those Google and IBM are developing, agrees that this presents a challenge. But he argues that his chosen technology’s head start will afford ample time and resources to tackle the problem.

Google and Rigetti have both said that in just a few years they could build a quantum chip with tens or hundreds of qubits that dramatically outperforms conventional computers on certain problems, even doing useful work on problems in chemistry or machine learning.