Silicon chip enables mass-manufacture of quantum technology that could lead the way to a completely secure mobile phone.

At the launch of the British Science Festival, 2012, scientists from the University of Bristol’s Centre for Quantum Photonics announced that they have developed a silicon chip that will pave the way to the mass-manufacture of miniature quantum chips.

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.

In the short term, the team expect to apply their new results immediately for developing quantum-secure communications chips that could find their way into mobile phones and laptop computers – increasing the security of online banking and internet shopping. The very nature of quantum mechanics means phones using these quantum chips would have completely secure encryption. Essentially, the phones would be un-hackable.

The Bristol-led team has taken the novel leap forward of developing quantum chips from silicon – thesame material routinely used en masse to build the tiny electrical processors in all computers and smart phones. However, unlike conventional silicon chips that work by controlling electrical current, these circuits manipulate single particles of light (photons) to perform calculations. These circuits exploit strange quantum mechanical effects such as superposition (the ability for a particle to be in two places at once) and entanglement (strong correlations between particles that would be nonsensical in our everyday world). The technology developed uses the same manufacturing techniques as conventional microelectronics, and can be economically scaled for mass-manufacture. These new circuits are compatible with existing optical fibre infrastructure and are ready to be deployed directly with the internet.

“Using silicon to manipulate light, we have made circuits over 1000 times smaller and more complex than current glass-based technologies. For the first time, we can mass-produce this kind of chip, 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” says Mark Thompson, deputy director of the Centre for Quantum Photonics. “This is very much the start of a new field of quantum-engineering, where state-of-the-art micro-chip manufacturing techniques are used to develop new quantum technologies and will eventuallyrealise quantum computers that will help us understand the most complex scientific problems.”

The researchers also believe that their device represents a new route to a quantum computer – a powerful type of computer that uses quantum bits (qubits) rather than theconventional bits used in today’s computers. Quantum computers will have unprecedented computational power for tasks including search engines and the design of new materials, pharmaceuticals and clean energy devices. This work, carried out in collaboration with Heriot-WattUniversity in Scotland and DelftUniversity in the Netherlands, is an essential step towards the miniaturisations of optical quantum computers.

Unlike conventional bits or transistors, which can be in one of only two states at any one time (1 or 0), a qubit can be in several states at the same time and can therefore be used to hold and process a much larger amount of information at a greater rate.

“It had previously been thought that a large-scale quantum computer will not become a reality for at least another 25 years,” says Jeremy O’Brien, director of the Centre for Quantum Photonics. “However, we believe that, using our new technology, a such a device, in less than 10 years, be performing importantcalculations that are outside the capabilities of conventional computers.”

Such a quantum computer based on this technology could be used to simulate processes which themselves are governed by quantum mechanics, such as superconductivity and photosynthesis. “Our approach will ultimately allow us to achieve component densities millions of times greater than current technologies, enabling miniature quantum circuits that could potentially fit inside a mobile phone, for example to enable quantum-secure communications for internet banking”, says Mark Thompson. Other applications include the development of ultra-fast and efficient search engines, and the design of high-tech materials and new pharmaceuticals.