A team of Australian scientists has made a breakthrough that brings a super internet based on ultra-powerful quantum computers a step closer.
The team, led by University of New South Wales researchers, is the first in the world to detect the spin, or quantum state, of a single atom using combined optical and electrical methods.
Quantum computers promise to deliver a massive increase in processing power over conventional computers by using a single electron or nucleus of an atom as the basic processing unit, a quantum bit, or qubit.
By performing multiple calculations simultaneously, quantum computers could be applied to economic modelling, fast database searches, modelling of biological molecules and drugs, and encryption and decryption of information.
They could become critical for providing secure communications for government, military, finance and health industries.
UNSW’s Professor Sven Rogge said the team’s technical feat was achieved with a single atom of the rare-earth element erbium embedded in silicon.
“This is a revolutionary new technique, and people had doubts it was possible. It is the first step towards a global quantum internet,” Professor Rogge said.
The study’s lead author, UNSW’s Dr Chunming Yin, said the new approach opened up the possibility of using light to couple the atoms, or qubits, together to form a quantum computer.
“Using light to transfer information in the quantum state is easier than doing it electrically. Ultimately this will lead to quantum communications over long distances,” Dr Yin said.
The researchers said it would be at least another decade before the potential of quantum computation was fully realised.
The study involved researchers from the UNSW, the Australian National University and the University of Melbourne and is published in the journal Nature.
“We have adapted magnetic resonance technology, commonly known for its application in chemical analysis and MRI scans, to control and read-out the nuclear spin of a single atom in real time,” Associate Professor Andrea Morello from the School of Electrical Engineering and Telecommunications (EE&T) at UNSW, said.
The nucleus of a phosphorus atom is an extremely weak magnet, which can point along two natural directions, either “up” or “down”.
In the strange quantum world, the magnet can exist in both states simultaneously, a feature known as quantum superposition.
“We achieved a read-out fidelity of 99.8 per cent, which sets a new benchmark for qubit accuracy in solid-state devices,” UNSW Scientia Professor Andrew Dzurak, who is also Director of the Australian National Fabrication Facility at UNSW, where the devices were made, said.
The accuracy of the UNSW team’s nuclear spin qubit rivals what many consider to be today’s best quantum bit, a single atom in an electromagnetic trap inside a vacuum chamber.
The development of this “Ion Trap” technology was awarded the 2012 Nobel Prize in physics.
“Our nuclear spin qubit operates at a similar level of accuracy, but it’s not in a vacuum chamber, it’s in a silicon chip that can be wired up and operated electrically like normal integrated circuits,” Professor Morello said.
In September 2012, the same UNSW team reported in Nature the first functional quantum bit based on an electron bound to a phosphorus atom embedded in silicon, “writing” information onto its spin and then “reading” the spin state back out.
With their latest result, the team has dug even deeper into the atomic structure to manipulate and measure the spin of its nucleus.
