Microsoft makes major bet on topological quantum computing
Microsoft has appointed Todd Holmdahl, previously responsible for the hardware design of the Xbox consoles, to lead a new team exploring a radically different approach to quantum computing. The idea is to build quantum bits ("qubits") out of a particle called the Majorana fermion. The idea is that these fermions, unlike the qubits used by IBM and Google, can be held in place by a superconducting plate rather than a magnetic field, and will be far more stable and scalable as a result. The only problem is that no one is completely sure that Majorana fermions actually exist.
“I am personally competitive, and my whole history is producing products,” he says. “We have line of sight to a commercial product.”

A quick glance at competing projects in quantum computing makes that kind of talk surprising. Google, IBM, and even some startups have already demonstrated prototype hardware capable of crunching data (see “10 Breakthrough Technologies: Practical Quantum Computing”). Microsoft isn’t yet close.

Holmdahl’s crew is chasing a different approach to quantum hardware based on manipulating a subatomic particle called the Majorana fermion, which the physics community isn’t 100 percent sure has ever been seen. It’s named after the man who predicted its existence, Italian physicist Ettore Majorana, who in 1938 emptied his bank account, caught a ferry, and disappeared without a trace.

While Google and IBM work on their next prototypes, Microsoft’s physicists are trying to build the first device that can conclusively isolate and encode a single digital bit of data with the particle Majorana predicted. Yet Holmdahl resists the suggestion that this means his company is unlikely to be first to market. “I think we actually will be,” he says.

Todd Holmdahl Courtesy of MSFT

Finicky hardware

Quantum computers are built out of devices known as qubits, which represent data using physics only apparent at very tiny scales. Tech companies and investors have sunk millions into the technology, because at the quantum scale, particles and information can do things that are flat out impossible in our human-sized reality. This means some calculations that would take centuries on a conventional computer can be done in seconds on a quantum computer. Google and others hope to use quantum computers to power up machine learning, and renting them out to solve problems in chemistry and materials science (see “Chemists Are First in Line for Quantum Computing’s Benefits”).

The catch is that although qubits can be built in various ways—the most advanced are based on superconducting metal circuits or metal ions floating inside magnetic fields—they are all unreliable because quantum states are so delicate. This month IBM announced the biggest chip made by the companies in the race for a general-purpose quantum computer—a chip with just 17 qubits. To do useful work, a quantum computer would likely need many thousands or millions of the devices.

Microsoft’s project is a giant bet on the idea that qubits based on the elusive Majorana fermion will be much more reliable, and thus easier to build into large collections that can do useful work. A theory known as topological quantum computing predicts that data written into the particles, by a device called a topological qubit, will be resilient to perturbations that would wipe out anything stored by a regular qubit (see “Microsoft’s Quantum Mechanics”).