IJS's achievement could lead to miniaturisation of microchips

Quantum chaos is a phenomenon that appears in electronic devices a few nanometres in size. It regulates the behaviour of electrons in computer chips and currently prevents scientists from making them any smaller, Mihailović explained.

To describe the phenomenon, one could use a comparison with billiards or quantum billiards, because electrons in a close space behave almost like balls on a billiards table - due to space constraints, they collide with the banks and other balls. The team managed to observe quantum billiards in artificial equilateral triangles whose sides measure as little as two nano metres, which corresponds to only 6 atoms.

Quantum chaos is a favoured problem for physicists and mathematicians to deal with, and the behaviour of a single quantum particle in a confined potential is predicted by the Schrödinger equation. But with multiple electrons confined to a small area, things get complicated.

Device for observing quantum chaos

The team led by Mihailović has managed to demonstrate quantum chaos in extremely small circuits for which they had to develop and manufacture a unique device in cooperation with the Jožef Stefan Institute and Nanocenter, which enables low temperatures and has laser lights and several tips for monitoring the path of electrons.

According to team member Jan Ravnik from the Paul Scherrer Institute in Switzerland, extremely small circuits the size of only a few atoms had to be created to observe the path.

"We succeed in making them by using ultra short laser pulses to transform a single atomic layer in tantalum disulphide", a material that is important in computer development, said Ravnik.

Measurements in the kind of conditions in which quantum computers operate

According to Ravnik, the trajectories of electrons were studied using a scanning tunnelling microscope at low temperatures and in ultra-high vacuum, which are the conditions in which quantum computers operate.

Moreover, to observe any quantum effects extremely low temperatures must be created to avoid thermal influences. The observation area must also be extremely small, because in a big space it would be impossible to keep track of the small particles.

Challenging calculations of electrons' trajectories

Jaka Vodeb from the Jožef Stefan Institute explained that calculating the trajectory of an electron in quantum billiard was a challenge for classical computers, but the team succeeded in calculating different trajectories that may be expected in differently sized structures observed experimentally.

The research, whose authors also include Yevhenii Vaskivskyi, Polona Aupič, Igor Vaskivskyi, Denis Golež, Yaroslav Gerasimenko and Viktor Kabanov, provides fresh insight into the understanding of the chaotic behaviour of electrons in atom-sized circuits. It could pave the way for further miniaturisation and use of new materials in future quantum and classic computers.

The article on the research has been published in Nature Communications.