Quantum computers 'one step closer to reality'

Researchers have inched a step closer towards developing the gen-next quantum computers with speeds that exceed the fastest supercomputers.
Researchers at Linkoping University in Sweden, in cooperation with German and American researchers, have succeeded in both initialising and reading nuclear spins, relevant to qubits for quantum computers, at room temperature.
A quantum computer is controlled by the laws of quantum physics; it promises to perform complicated calculations, or search large amounts of data, at a speed that exceeds by far those that today's fastest supercomputers are capable of.
"You could say that a quantum computer can think several thoughts simultaneously, while a traditional computer thinks one thought at a time," says Professor Weimin Chen, one of the main authors of the study.

A traditional computer stores, processes and sends all information in the form of bits, which can have a value of 1 or 0. But in the world of quantum physics, at the nano- and atomic level, other rules prevail and a bit in a quantum computer - a qubit - can have any value between 1 and 0.
A spin-based qubit makes use of the fact that electrons and atomic nuclei rotate around their own axes - they have a spin.

The first step in building a quantum computer is to assign each qubit a well-defined value, either 1 or 0. Starting, or initiating, the spin-based qubits then requires all the atomic nuclei to spin in the same direction, either 'up' or 'down'.

The most common method for polarising nuclear spin is called dynamic nuclear polarisation; this means that the electrons' spin simply influences the nucleus to spin in the same direction.
The main problem is that the spin orientation in the electrons can easily be lost at room temperature, since it is sensitive to disruptions from its surroundings.
Researchers have now discovered a way of getting around this problem.
With the help of the spin filter that works at room temperature, they have now succeeded in producing a flow of free electrons with a given spin in a material - in this case GaNAs (gallium nitrogen arsenide).

The spin polarisation is so strong that it creates a strong polarisation of the nuclear spin in extra Ga atoms that are added as defects in the material - and this takes place at room temperature.
This is the first time that strong nuclear spin polarisation of a defect atom in a solid is demonstrated at room temperature by spin-polarised conduction electrons.
The study was published in the journal Nature Communications.