Emil Sierda, who was in charge of conducting the experiments at Radboud University: ‘A few years ago we had this crazy idea to build a quantum simulator. We wanted to create artificial molecules that resembled real molecules. So we developed a system in which we trapped electrons. Electrons surround a molecule like a cloud, and we used those trapped electrons to build an artificial molecule.’ The results the team found were astonishing. Sierda: ‘The resemblance between what we built and real molecules was uncanny.’
Alex Khajetoorians, head of the Scanning Probe Microscopy (SPM) department at Radboud University: ‘Making molecules is difficult enough. What is often harder, is to understand how certain molecules react, for example how they change when they are twisted or altered.’ How molecules change and react is the basis of chemistry, and leads to chemical reactions, like the formation of water from hydrogen and oxygen.
‘We wanted to simulate molecules, so we could have the ultimate toolkit to bend them and tune them in ways that are nearly impossible with real molecules. In that way we can say something about real molecules, without making them, or without having to deal with the challenges they present, like their constantly changing shape.’
Using this simulator, the researchers created an artificial version of one of the basic organic molecules in chemistry: benzene. Benzene is the starting component for a vast amount of chemicals, like styrene, which is used to make polystyrene. Khajetoorians: ‘By making benzene, we simulated a textbook organic molecule, and built a molecule that is made up of elements that are not organic.’ Above that: the molecules are ten times bigger than their real counterparts, which makes them easier to work with.
The uses of this new technique are endless. Daniel Wegner, assistant professor within the SPM department: ‘We have only begun to imagine what we can use this for. We have so many ideas that it is hard to decide where to start.’
By using the simulator, scientists can understand molecules and their reactions much better, which will help in every scientific field imaginable. Wegner: ‘New materials for future computer hardware are really hard to make, for instance. By making a simulated version, we can look for the novel properties and functionalities of certain molecules and evaluate whether it will be worth making the real material.’
In the far future, all kinds of things may be possible: understanding chemical reactions step by step like in a slow-motion video, or making artificial single-molecule electronic devices, like shrinking the size of a transistor on a computer chip. Quantum simulators are even suggested to perform as quantum computers. Sierda: ‘But that’s a long way to go, for now we can start by beginning to understand molecules in a way we never understood before.’
The research was conducted by a Radboud University collaboration between the groups of Malte Rösner (Theory of Condensed Matter), Mikhail Katsnelson (Theory of Condensed Matter), Gerrit Groenenboom (Theoretical Chemistry), Daniel Wegner (SPM) and Alex Khajetoorians (SPM).