Public Release: 

Another step towards understanding the quantum behavior of cold atoms

A UPV/EHU-University of the Basque Country researcher has explored the quantum effects produced when bosons and fermions are mixed at a very low temperature

Elhuyar Fundazioa


IMAGE: The UPV/EHU-University of the Basque Country physicist Eneko Malatsetxebarria has explored the quantum effects produced when bosons and fermions are mixed at a very low temperature. view more

Credit: UPV/EHU

This news release is available in Spanish.


The experiments carried out on cold atoms are very important for understanding quantum physics.In actual fact, they provide anopportunity to observe quantum effects directly. Cold atoms are known as quantum simulators for that very reason. In the words of Eneko Malatsetxebarria, who has done his thesis in this field at the DIPC (Donostia International Physics Center) and at the Centre for Materials Science, "it is a very powerful tool for understanding the behaviour of condensed matter. It is not like before when quantum effects were something that occurred inside a black box; now we are capable of manipulating atoms almost as we want and observing the quantum effects."

In any case, experiments with cold atoms are complicated. Alkaline gas atoms have to be cooleddown to near to absolute zero (-273.15 ºC), and this calls for very complex equipment and techniques equipped with laser and magnetic traps.And this is very costly. "Worldwide, there'll be 30 labs at the most conducting these experiments at the highest level," added Malatsetxebarria.

That is why it is so important to conduct theoretical research in this field. By making use of the theoretical tools of quantum physics, it is possible to explore fields that go beyond the technical obstacles of experiments, and thus understand the special effects that arise out of atom interaction.This has been the field of work of Malatsetxebarria and his PhD thesis supervisor, Miguel Angel Cazalilla. They have been in contact with experimental groups in Germany and Japan, and taking the work of these researchers as the basis, they have put forward proposals for new experiments.

Firstly, they have determined the conditions under which boson and fermion atoms can be mixed. It can be said that when quantum effects are taken into consideration, elementary particles are of two types: bosons and fermions. As atoms are made up of these particles in different combinations, they will also be of one type or the other, boson or fermion ones, and as a result, their quantum behaviour will be different. So far, very few experiments have been conducted involving the mixing of bosons and fermions. "Sometimes they are like oil and water and they won't mix; other times, the attraction force is too strong and the system collapses," pointed out Malatsetxebarria. In a paper in the prestigious journal Physical Review he demonstrated the conditions under which they can be mixed. In the system he analysed in the journal, bosons are found in a single dimension, like a line of marbles; while fermions can be found in three dimensions as a kind of cloud. There's nothing random about the choice of that geometry.When passing from one to three dimensions, the interaction between the atoms is qualitatively different on a quantum level too, which is why experimental groups have also recognised their importance when exploring the systems.

Fermion and boson interactions






The author

EnekoMalatsetxebarria-Elizegi (Bilbao, Basque Country, 1984) graduated in Physics at the Faculty of Sciences of the UPV/EHU-University of the Basque Country. He went on to do a Master's in Nanosciencerun by the UPV/EHU in conjunction with the DIPC (Donostia International Physics Center) and Nanogune. He did his PhD at the DIPC and at the Centre for Materials Science. He spent a period of time at the Physics department of Georgetown University in Washington, D.C. to expand his field of research. He did his PhD thesis on "Bosons and Fermions in Mixed-dimensional Optical Lattices: Phase equilibria and Quantum Phase Transitions", under the supervision of Miguel Angel Cazalilla.
