Ready for topologically based quantum computers?
Israeli physicists have discovered bizarre 'quasiparticles' which have one quarter the charge of an electron, and may be useful in quantum computing. Quasiparticles are formed within a group of electrons and behave as if they are particles. But they only have a fraction of the charge of an electron, according to lead researcher Merav Dolev from the Weizmann Institute of Science in Israel, who announced the discovery. Curiously no single particle can have a fraction of electric charge.
Until now, researchers have only been able to form quasiparticles with one-third, one-fifth or one-seventh of the charge on an electron. Quasiparticles with even denominators, such as one-quarter or one-sixth, are expected to behave completely differently to quasiparticles with odd denominators.
In this study, the researchers trapped a 'soup' of electrons in an extremely pure sample of gallium arsenide, so that the electrons could only move in two directions – forward and backward, and side to side, but not up and down. As they also reported in a paper in the British journal Nature this year, they then placed this sample in a magnetic field. In this precise set-up, with extremely pure gallium arsenide, researchers could see these quarter-charged quasiparticles.
It's even denominator quasiparticles such as one-quarter, that are interesting, because scientists expect the order in which they interact changes the outcome. Switch quasiparticle A with quasiparticle B, then switch B with C, is not the same as switching B with C then A with B.
"It is very non-intuitive," said Dolev. "All of the 'regular' particles – which is what we are used to – do not behave like that." Quasiparticles with odd denominations of electron charge do not share this curious behaviour. The result is that a quasiparticle can 'remember' the path it has taken. Dolev expects this property to be exploited in an exotic type of quantum computer called a 'topological quantum computer'.
The computing would be done "by rotating quasiparticles, one around the other." Dolev said. "All you care about, then, is which quasiparticle went around which, not the exact path. This is what makes it 'topological', since you only care about the topology of the path."
Computing is based on strings of bits taking the value 1 or 0 curently done by transistors. In a quantum computer, the bits would be particles linked together by quantum behaviour termed 'qubits' or quantum bits. In topological quantum computers a bit could be made from two quasiparticles.
In other types of quantum computing, as linking quantum bits with lasers, the system is strongly affected by its environment. An ever-so-slight movement stops the system from working. But because of the path of these quasiparticles is not important, a topological quantum computer would be much more robust.
"The possibility of producing a topologically based quantum computer based on these quasiparticles is interesting," commented physicist Jeff McCallum, from the University of Melbourne. "[But] there is plenty of room for more competitors in the quantum computer race, and no clear winner in the field yet."
The first quantum computer may be here in less than 20 years :would be many times more powerful than current supercomputers, rapidly solving problems that currently take many years to complete.
Source:http://www.cosmosmagazine.com