Universiteit Leiden

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Light on the quantum computer

Physicist Martin van Exter works with light at nanoscale, at the forefront of nanocomputer research. But as Director of Education he also has a vision for physics teaching. Inaugural lecture 18 November.

'I was the kind of child that loved to take things apart to see what was inside, much to the dismay of my parents,'  Martin van Exter explains at the start of his inaugural lecture. There are two types of physicists: the theoretician and the experimenter. Martin van Exter belongs to this last group, and his field is quantum optics. 

The cornerstone of one of his research projects is the optical quantum dot. These are minuscule discs of one type of semiconductor material, enclosed in another semiconductor material (computer chips are made of semiconductor material).  A quantum dot works like a large, man-made atom. 

If you add two mirrors, you have a nano-device that can be manipulated using individual photons, or light particles. By adding one extra electron to the quantum dot, you can use it as a qubit, the fundamental building block of the quantum computer. 

Controlling quantum dots 

Van Exter's group is working on perfecting control of their quantum dot using photons so that they can communicate with one another and make calculations. 'Playing more quantum games  - and more complex ones too,' is how Van Exter once described it. For the time being it is purely fundamental research. Valorisation, the application of research results by businesses or other research institutes, is still a long way in the future.  

Van Exter is encouraged by the fact that Ben Feringa in Groningen won the Nobel Prize this year for his work on nano-motors. 'If we don't do enough fundamental research now, we can't expect to achieve any major technological breakthroughs in the future. And that fundamental research should be as broad as possible. A lot of successful applications emerge from discoveries that you weren't actually looking for. Trying to apply business models to valorisation makes things difficult. My message to goverment is to let scientists play more!'  

Fewer contact hours, more self-study

As Director of Education, Van Exter also has a vision for teaching students of natural sciences: 'Studying science subjects is all about becoming familiar with new ideas, concepts and techniques. What's essential is that students get to explore new knowledge independently and that they learn to look at things from different perspectives. I'm in favour of fewer contact hours and more time for self-study.' Rather than passive lectures, he envisages types of teaching where students get to work with the study material themselves, based on textbooks, or even YouTube films, and that they come together in tutorials to discuss issues with their lecturers at a higher level. 

He sees in this more active way of interacting with the study material a solution for a persistent problem: students who 'cram' for exams and then promptly forget what they've learned. Some kind of measure to counter this wouldn't do any harm. 'Introducing an annual progress test could help; something like a test on the course material from all the subjects in the curriculum.' 

What is the ultimate aim of a natural sciences programme? Van Exter: 'What do we want to give our natural sciences students? Well, first of all a particular way of thinking that translates into the ability to solve problems. I'm a firm fan of the 'less is more' approach: rather a modest, but solid and readily available basic understanding with the possibility of building on that using books and internet, than more extensive but shaky knowledge.' 

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