Two-photon quantum walk puts real quantum computers within reach

We are within ten years of a quantum computer than can outperform traditional machines according to a team of researchers at the University of Bristol.

A team of researchers has developed a new photonic chip capable of performing a "quantum walk" with two photons. Lead researcher Professor Jeremy O’Brien, Director of the Centre for Quantum Photonics says that the work could have significant implications for how quickly a real-world quantum computer is up and running, in part because the breakthrough from one to two photons paves the way for quantum walks with many more than two photons.

In the press announcement, he’s quoted as saying: “Using a two-photon system, we can perform calculations that are exponentially more complex than before. 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.”

The quantum walk experiment – the simulation of the random movement of a quantum particle - has been performed before, but with just one photon. The jump from one photon to two is not trivial, the researchers say, but scaling up from two to three and beyond is far easier.

“Each time we add a photon, the complexity of the problem we are able to solve increases exponentially, so if a one-photon quantum walk has 10 outcomes, a two-photon system can give 100 outcomes and a three-photon system 1000 solutions and so on,” Professor O’Brien explains.

In the short term, the results will be useful for developing new simulation tools in the lab, but long 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”.

The research is published in Fri 17th issue of the journal Science.