A team from the Hanns-Christoph Nägerl Institute for Experimental Physics of the University of Innsbruck, Austria, has observed tunneling dynamics in a system of quantum particles transmitted through five potential barriers.
Quantum tunneling refers to the quantum-mechanical effect of transitioning through an energy state that is forbidden in the context of classical mechanics.
For example, there is a minimum velocity needed for a ball to roll up and over a hill, without which the ball will remain or return to its present location. In quantum mechanics, however, objects do not behave like classical objects. Instead, objects exhibit wavelike behaviors.
Returning to the example of a ball, the ball’s wave function (which describes all the characteristics of the ball’s wavelike behavior) would describe the probability of finding the ball at the other side of the hill. That the ball could be found on the other side, describes the effect of quantum tunneling: in essence, the ball could tunnel through the hill.
Interesting, the quantum tunnel effect explains a number of real-life phenomena including radioactive decay, fusion reactions such as the ones that occur in the Sun and describes how scanning tunneling microscopes work.
Now, a team from the Hanns-Christoph Nägerl Institute for Experimental Physics of the University of Innsbruck, Austria, has observed tunneling dynamics in a system of quantum particles transmitted through five potential barriers. Amazingly, one particle could not penetrate a barrier; however, the particles seemed to assist each other in moving through the barriers.
The experiments were conducted by placing Cesium gas atoms just above absolute zero temperature into an optical lattice of multiple tunneling barriers. Given that the temperatures are so low, the gas molecule kinetic energies were similarly very small. The only way to then move through the lattice was via tunneling through the barriers after a directing force had been applied.
The physicists were able to uncover how the interactions between particles and the strength of the directed force determine the number of barriers the particles can penetrate, which leads to discrete resonances corresponding to the number of barriers penetrated.
In the future, scientists hope to explore how tunnel processes in ultra cold lattice systems as the one described can be used in a variety of physical or even biological systems.
