Researchers accidentally solve decades-old puzzle that could help create quantum computers

Scientists have accidentally solved a decades-old quantum puzzle that could lead to new breakthroughs in entirely different kinds of computers.

The breakthrough discovery not only solves a mystery that has perplexed scientists for more than half a century, but could allow researchers new capabilities when they are building quantum computers and sensors.

It means that scientists can finally control the nucleus of one single atom, using electric fields, a feat that was impossible before.

The research actually seizes on research that was first proposed by scientists 60 years ago. But, until now, it had remained only theoretical, and eluded anyone who tried to actually put it into action.

Scientists now hope that the discovery can be used to more precisely build quantum computers, and could be used to shed light on some of the mysteries of quantum science.

"This discovery means that we now have a pathway to build quantum computers using single-atom spins without the need for any oscillating magnetic field for their operation," says the University of New South Wales' Scientia Professor of Quantum Engineering Andrea Morello.

"Moreover, we can use these nuclei as exquisitely precise sensors of electric and magnetic fields, or to answer fundamental questions in quantum science."

At the moment, a nuclear spin of this kind is controlled with magnetic fields. But the ability to do so with electric fields has "far-reaching consequences", the researchers said. Magnetic fields must be generated using large coils and high currents and need larger spaces; the equipment needed to generate electric fields is much smaller and more controlled.

"Nuclear Magnetic Resonance is one of the most widespread techniques in modern physics, chemistry, and even medicine or mining," says Professor Morello. "Doctors use it to see inside a patient's body in great detail while mining companies use it to analyse rock samples.

"This all works extremely well, but for certain applications, the need to use magnetic fields to control and detect the nuclei can be a disadvantage."

Changing away from that technique is like the difference between moving a billiard ball by picking up and shaking the whole table around, said Professor Morello – it will move, but make a mess of the rest of the ball's place. The electric resonance can be used to push the ball exactly where it needs to be.

The technique was first proposed by another researcher in 1961. But researchers stumbled back on it by accident, they said, after it had been left ignored for more than half a century because it had been too difficult to demonstrate in practice.

Now the researchers hope to be able to use their new way of controlling atoms for a variety of different breakthroughs.

"This landmark result will open up a treasure trove of discoveries and applications," said Professor Morello.

"The system we created has enough complexity to study how the classical world we experience every day emerges from the quantum realm. Moreover, we can use its quantum complexity to build sensors of electromagnetic fields with vastly improved sensitivity. And all this, in a simple electronic device made in silicon, controlled with small voltages applied to a metal electrode!"