Scientists take one step closer to a quantum computer

26 Sep 2019

A quantum processor semiconductor chip connected to a circuit board. Image: J Adam Fenster/University of Rochester

New research from Purdue University and the University of Rochester edges towards the development of a fully functioning quantum computer.

In a paper published in Nature, scientists have demonstrated their method of relaying information by transferring the state of electrons, bringing science one step closer to creating a fully functional quantum computer.

A fully realised quantum computer could revolutionise applications of technology with much faster and more efficient processors, sensors and communication devices. However, before this revolution can come into effect, scientists must overcome the challenge of transferring information and correcting errors within a quantum system.

‘Our research shows this is now a viable approach to send information over long distances’

All computers, from your desktop to your smartphone to a potential quantum computer, have to perform error correction. In a regular computer, copies of bits mean an error can be corrected when one bit goes bad. Quantum bits, or qubits, however, cannot be copied.

“You have to be very clever about how you correct for errors. What we’re doing here is one step in that direction,” said John Nichol, assistant professor of physics at University of Rochester.

Switching electron states

In an attempt to facilitate error correction in a quantum computer, researchers from the University of Rochester and Purdue University forced a phenomenon whereby two electrons pushed together will switch states.

An electron is like a bar magnet with a north and south pole, the direction of which is known as its quantum state. “If you have one electron that’s up and another electron that’s down and you push them together for just the right amount of time, they will swap,” explained Nichol. “They did not switch places, but their states switched.”

To force this switch, Nichol and his colleagues first cooled a semiconductor chip to extremely low temperatures. Then, using nanoscale semiconductors known as quantum dots, they trapped four electrons in a row. They then moved these electrons into close contact until their states switched.

“There’s an easy way to switch the state between two neighbouring electrons, but doing it over long distances – in our case, it’s four electrons – requires a lot of control and technical skill,” said Nichol. “Our research shows this is now a viable approach to send information over long distances.”

‘An important step’

Michael Manfra, a professor of physics and astronomy at Purdue University, added: “This experiment demonstrates that information in quantum states can be transferred without actually transferring the individual electron spins down the chain.

“It is an important step for showing how information can be transmitted quantum-mechanically, in manners quite different than our classical intuition would lead us to believe.”

Earlier this month, Google reportedly achieved ‘quantum supremacy’, in that a quantum computer outperformed a classical one in an experiment. However, experts cautioned that this does not mean the age of practical quantum computing is upon us.

“A quantum computer needs to have many qubits, and they’re really difficult to make and operate,” said Nichol. “The state-of-the art right now is doing something with only a few qubits, so we’re still a long ways away from realising the full potential of quantum computers.”

But, while a quantum computer in every home appears to be a faraway concept, Nichol likened this scepticism to that around early computers. “If you had asked that question of IBM in the 1960s, they probably would’ve said no, there’s no way that’s going to happen. That’s my reaction now. But who knows?”

Future applications

Practical applications of a powerful quantum computer that can simulate the behaviour of matter at a molecular level include developing new energy sources, studying the conditions of planet and galaxies, or the discovery of new drug therapies. Quantum computers would also be capable of faster database searches and advances in cryptography.

“It turns out that almost all of modern cryptography is based on the extreme difficulty for regular computers to factor large numbers,” said Nichol. “Quantum computers can easily factor large numbers and break encryption schemes, so you can imagine why lots of governments are interested in this.”

The University of Rochester recently received a $4m grant from the US Department of Energy to support research in quantum information science. Meanwhile, in Ireland, researchers at the Tyndall National Institute have said an Irish quantum research centre could still play a major part in this burgeoning technology market, which is estimated to be worth $15trn by 2030.

Elaine Burke is the host of For Tech’s Sake, a co-production from Silicon Republic and The HeadStuff Podcast Network. She was previously the editor of Silicon Republic.