One more step to simulate the quantum world

A study has compared the frequency with which quantum tunneling occurs in reality with theoretical predictions to refine our understanding

Quantum tunneling is a peculiarity of quantum mechanics. This allows particles to pass through obstacles that would normally be too difficult to overcome. Now, a team of Austrian physicists has observed the strange phenomenon for the first time. Details of the research were published in Nature. In chemistry, it is usual that the construction of molecules requires a certain cost of energy. However, quantum theory also provides exceptions. In extremely rare cases, it is possible for atoms in close proximity to force their way through this energy barrier and effortlessly connect.

quantum tunnel A team of physicists from the University of Innsbruck led by Robert Wild conducted an experiment that measured the fusion of deuterium ions with hydrogen molecules. At the end they saw the quantum tunneling in action, being the world’s first experiment of its kind. Understanding the role that quantum tunneling plays in the construction and rearrangement of molecules could have important ramifications. For example, it would help us to make better calculations of the release of energy in nuclear reactions, such as those of hydrogen in stars and fusion reactors.

Quantum waves are the ghosts that drive the strange behavior of objects like electrons, photons, and even entire groups of atoms. In addition, they are responsible for these objects occupying various possible positions and not just being located in a precise place. Such blurring is negligible for larger objects like molecules, humans, and galaxies. But as we get closer to individual subatomic particles, the range of possibilities expands. This forces the location states of various quantum waves to overlap. One such region for an electron might be within the bonding zone of a chemical reaction, welding neighboring atoms and molecules together without the boom-bump-crush of heat or pressure. Phenomenon known as the quantum tunneling effect.

The experiment To carry out this experiment, the researchers cooled the negative deuterium ions to a temperature that stopped them. Next, they introduced a gas made of hydrogen molecules. Without heat, the deuterium ion was much less likely to have the energy to force the hydrogen molecules to rearrange the atoms. Even so, it also forced the particles to sit quietly close to each other, giving them more time to join together through the tunnel.

As a result, the possible reactions in the trap took about 15 minutes. Then, the amount of hydrogen ions formed was determined. From their number, it could be deduced how often a reaction had occurred. The figure was just over 5 x 10-20 reactions per second taking place in every cubic centimeter. This is about one tunneling event for every hundred billion collisions. Although the frequency is very low, the experiment supports the previous model. Quantum tunneling plays quite an important role in a wide range of nuclear and chemical reactions. For that reason, getting a precise control of the factors in play gives us a stronger foundation for our predictions about him.