Quantum simulations are useful for everyone. This is the message Arthur La Rooij wants to convey in his PhD thesis, which he will defend on Friday 24 February at the University of Amsterdam.
La Rooij built a new machine which can be used to control quantum mechanical cold atoms using tiny magnets of only 200nm on a chip. As a result, physicists can compare the behavior of these atoms to that of electrons in materials. Using this technique, atoms can be brought two times closer together than the current standard.
La Rooij developed an experiment in which quantum mechanical particles are placed in so-called magnetic lattices. La Rooij: 'I am interested in lattices of atoms because the same kind of physics can be applied to materials.'
To better understand the quantum lattices that appear in materials, La Rooij experimented with atoms that he could completely control. His main goal was to make the lattices smaller. 'Using the technique I developed and the machine I built, we can bring the confined atoms closer together. This means that they interact more strongly, and that it is easier for them to move inside the lattice. In this way, we can perform quantum simulations of interesting systems that look much more like the materials we try to understand. The scale is fifty times smaller than in our previous experiments, and twice as small as the current standard in physics. If we succeed in catching atoms in these lattices, we will have created a unique, ultra-small atomic lattice.'
La Rooij explains how the atoms will be placed in lattices in practice. 'Imagine a completely empty space, which has been pumped to a vacuum. Into this space, we release a number of particles coming from a small furnace. The particles are then illuminated from all directions by lasers. In this way, the particles are slowed down: the lasers are used to remove energy from the atoms. Ultimately, the atoms will come to a complete halt inside the cloud of gas. Once this has been achieved, we can put them in a lattice.' In La Rooijs experiment, it is then possible to enlarge this lattice, or for example to make it more granular, to investigate what effect these changes have on the atoms.
This knowledge may have practical applications in the future for materials which have a lattice structure, like salt or certain metals. 'My favourite problem in the quantum world concerns the interactions of electrons in superconducting materials.', La Rooij explains.' These metals could transport energy very efficiently… if they would work at room temperature. Currently, they only work at temperatures below -100 ºC or under very high pressure.' It will take time for physicists to reach this stage, but once they can? 'Then we could transport electricity for free, saving an enormous amount of energy and an enormous amount of money. It would be incredible if we can achieve that.'
A. L. La Rooij: Nanoscale Magnetic Atom Chips for Quantum Simulation. Supervisor is Prof. H.B. van Linden van den Heuvell. Second supervisor is Dr R.J.C. Spreeuw.
The defense will take place on Friday 24 February at 13:00. Location: UvA Aula: Singel 411, Amsterdam.