September 6, 2012

Quantum Circuits Built with Conventional Silicon Materials

Robert Gelber

With industry experts predicting the eventual demise of Moore’s Law, the long-term prospects for silicon-based computing appear rather bleak. However, a research project at the University of Bristol may give the technology a second life. The institution’s center for quantum photonics announced a breakthrough process that uses conventional semiconductors to create quantum chips.

Researchers have proposed quantum computing can be implemented using photons – essentially particles of light.  But this typically requires the use of optical fibers, or more recently, exotic waveguide circuits made of silica and silicon-oxy-nitride.  All of these are rather inconvenient to use when fabricating mass-produced computer chips.

To get around that problem, the researchers have developed integrated quantum photonic waveguide circuits using silicon-on-insulator materials. As explained in the announcement, the main advantage of this approach is that these waveguides circuits are compatible with those used in traditional microprocessors.

The leap from using glass-based circuits to silicon-based circuits is significant because fabricating quantum circuits in silicon has the major advantage of being compatible with modern microelectronics. Ultimately this technology could be integrated with conventional microelectronic circuits, and could one day allow the development of hybrid conventional / quantum microprocessors.

Using these structures, researchers created circuits capable of performing quantum calculations, enabling a different type of computing than that delivered by conventional binary logic. Instead of assigning bits with 1’s and 0’s, quantum computers use qubits, which have the ability to assume the value of 1, 0 or both, otherwise known as superposition. As the number of qubits increase, the potential computational capacity grows exponentially.

“Using silicon to manipulate light, we have made circuits over 1000 times smaller than current glass-based technologies. It will be possible to mass-produce this kind of chip using standard microelectronic techniques, and the much smaller size means it can be incorporated in to technology and devices that would not previously have been compatible with glass chips,” said Mark Thompson, deputy director of the Center for Quantum Photonics at Bristol.

Containing components as small as 10 micrometers, the silicon quantum chip was able to perform quantum interference and manipulation operations. Given this development and other advances in the field of quantum computing, Bristol’s research team believes the components now exist to build a fully functional quantum processors.

Full story at Bristol University newsroom