Scientists have developed a computer chip that could pave the way for a new generation of powerful 'quantum' computers.

The photonic chip, built by scientists from Bristol's Centre for Quantum Photonics, uses light rather than electricity to pass information.

The breakthrough could lead to 'quantum' computers capable of performing complex calculations and simulations that are impossible for today's computers.

The researchers believe that their device represents a new route to a quantum computer - a powerful type of computer that uses quantum bits (qubits) rather than the conventional bits used in today's 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 is widely believed that a quantum computer will not become a reality for at least another 25 years,' says Professor Jeremy O'Brien, Director of the Centre for Quantum Photonics.

'However, we believe, using our new technique, a quantum computer could, in less than ten years, be performing calculations that are outside the capabilities of conventional computers.'
The technique developed in Bristol uses two identical particles of light (photons) moving along a network of circuits in a silicon chip to perform an experiment known as a quantum walk.
Quantum walk experiments using one photon have been done before and can even be modelled exactly by classical wave physics.

But rhis is the first time a quantum walk has been performed with two particles and the implications are far-reaching.
'Using a two-photon system, we can perform calculations that are exponentially more complex than before,' says Prof O'Brien.

'This is very much the beginning of a new field in quantum information science and will pave the way to quantum computers that will help us understand the most complex scientific problems.'
In the short term, the team expect to apply their new results immediately for developing new simulation tools in their own lab.
In the longer term, a quantum computer based on a multi-photon quantum walk could be used to simulate processes which themselves are governed by quantum mechanics, such as superconductivity and photosynthesis.