A ‘game-changing’ device that could pave the way for development of practical quantum computers has been created by Australian researchers.
Developed by a team from Australia’s National Fabrication Facility, the so-called logic gate is based on conventional silicon technology, which makes it suitable for commercial manufacturing of quantum computing chips.
A logic gate is a logically controlled switch that allows calculations to be made. In conventional computers it uses different voltage levels to represent one of the two binary conditions – ones and zeros. In quantum computing, such a device exploits the ability of sub-atomic particles to exist in more than one state at the same time. This ability allows performing multiple calculations in parallel, potentially leading to the substantially increased speed and performance expected from quantum computers.
"We've demonstrated a two-qubit logic gate - the central building block of a quantum computer - and, significantly, done it in silicon,” said Professor Andrew Dzurak, from the Australian National Fabrication Facility at the University of New South Wales.
"Because we use essentially the same device technology as existing computer chips, we believe it will be much easier to manufacture a full-scale processor chip than for any of the leading designs, which rely on more exotic technologies.”
On a physical level, bits are typically stored on a pair of silicon transistors, one of which is switched on while the other is off.
In a quantum computer, data is encoded in the ‘spin’, or magnetic orientation, of individual electrons. Not only can they be in one of two ‘up’ or ‘down’ spin states, but also in a superposition of up and down.
The key step taken by the Australian scientists was to reconfigure traditional transistors so that they can work with qubits instead of bits.
"The silicon chip in your smartphone or tablet already has around one billion transistors on it, with each transistor less than 100 billionths of a metre in size,” explained lead author of the device Menno Veldhorst, from the University of New South Wales.
"We've morphed those silicon transistors into quantum bits by ensuring that each has only one electron associated with it. We then store the binary code of zero or one on the 'spin' of the electron, which is associated with the electron's tiny magnetic field."
The team has secured a patent on a full-scale quantum computer chip that could perform functions involving millions of qubits.
A practical quantum chip could have a huge impact in areas where classical computers face an uphill struggle such as weather forecasting, stock market operations, drug development or code-breaking and encryption.
The research is described in the latest issue of the journal Nature.