Scientists clear quantum computing hurdle

Researchers have devised a new way to prevent neighboring quantum bits from interfering with each other, bringing large-scale quantum computing one step closer to reality.

Illustration by Jake Turcotte
This illustration looks nothing like an actual atom. The electrons that orbit an atomic nucleus are actually in all possible places at the same time.

Large-scale quantum computing, that is, leveraging the seemingly paradoxical behavior of subatomic particles to develop blazingly fast computers, is now one step closer to reality, now that scientists have found a way to better control how these particles behave. 

Normal computers store information in binary digits, or bits. A bit can have only one of two values, most commonly represented by a 0 or a 1. Bits can be embodied in levers, punch cards, vacuum tubes, magnetic strips, tiny pits on compact discs, electrical capacitors, or any thing that can have two distinct states.  

Quantum computers, by contrast, use quantum bits, or qubits, which arise out of the properties of elementary particles. At the atomic and subatomic scales, the rules seem to be different from those for larger objects. An electron, for instance, exists in more than one place at the same time. The same goes for the magnitude of its angular momentum, or "spin," which can have more than one value at the same time.   

This behavior, called quantum superposition, allows qubits to have values of 0, 1, or both, all at the same time, creating the potential for computers that can carry out incredibly complex calculations in a fraction of the time that it would take a traditional computer. One of the most promising ways to create quantum computer chips is to use electrodes to control and harness the superposed spins of electrons bound to phosphorous atoms within silicon chips. 

But researchers attempting to do this kept running into a problem: When you change the spin of one electron, you end up affecting the spin of the ones next to it. Think of it like a garage door opener that opens every garage on the street.

In the current issue of the journal Nature Communications, scientists at the University of New South Wales in Sydney, Australia, working with theorists at Sandia National Laboratories in New Mexico say they have found a way around this inadvertent quantum jostling

“It is a daunting challenge to rotate the spin of each qubit individually,” says Holger Büch, a UNSW doctoral candidate and lead author of the new study, in a press release.

Mr. Büch and his colleagues found that, if each electron is bound to a different number of phosphorous atoms than its neighbor, each will respond differently to a tuned electromagnetic frequency, allowing each qubit to be distinguished from the ones around it.

“This is an elegant and satisfying piece of work,” said UNSW Professor Michelle Simmons, Büch's Ph.D advisor. "This first demonstration that we can maintain long spin lifetimes of electrons on multi-donor systems is very powerful. It offers a new method for addressing individual qubits, putting us one step closer to realising a practical, large-scale quantum computer."

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to