Renema obtained his PhD in Leiden and will use his Rubicon grant to move to Oxford University. He tells us enthusiastically about his research:

"My research is about building a non-universal quantum computer. This means a quantum computer that can only perform a specific calculation. The motivation behind this is that it appears to be extremely difficult to build a universal quantum computer; this is a generational project of the scale of the Manhattan project, or of building the firsst nuclear fusion reactor.

"For that reason, it’s interesting to see in the meantime if we could build a machine that can execute some calculation—which is difficult in classical terms—more efficiently based on quantum technology. Up until now, our primitive quantum calculations have always been easily imitated by a classical computer. For example factorizing the number 15, using a quantum computer will take years of work plus a lab full of people, while with pen and paper you quickly find that 3 multiplied by 5 gives 15.

"Our goal is to make a quantum calculation which is not that easily reproducible on a regular computer. That calculation doesn’t even have to be necessarily interesting in terms of applications. It’s all about showing that a quantum calculation can in fact be faster than its classical counterpart.

"There is a specific proposal for such a non-universal quantum computer; the Boson Sampler. A Boson Sampler is a network of channels that are placed in a glass plate. When two of those channels meet, a photon (light particle) can jump over from one channel to the other. Now if there is a photon in each of the channels, they will influence each other’s path in a way that can only be described by quantum mechanics.

"This leads to a level of complexity with which a classical computer cannot keep up. However, in the experiment this happens automatically: the machine 'calculates' its own outcome efficiently. My ultimate goal is to extend the existing Boson Sampler to a version that is large enough so that a classical computer won’t be able to keep up with its speed. Then, we have demonstrated that quantum calculators are indeed fundamentally different from classical computers."

Rubicon is an NWO funding instrument for scientists who have recently obtained their PhD, to gain experience at foreign top institutes, as stepping stone towards a scientific career.