A team of researchers from the University of Toronto has found a way to measure how long a quantum tunneling or tunneling effect takes. In their paper published in the journal Nature, the group describes the experiments they conducted and the results they found when trying to measure how long the process takes under certain circumstances.
In a sense, the tunneling effect is a phenomenon in which a particle passes through an energy barrier, despite the lack of energy for this process. Scientists don’t really know how it works, but they still found a use for it. For example, this process is used in the design of scanning tunneling microscopes. One factor in the tunneling effect that has been debated by physicists over the past century is how long it takes for a particle to pass through an energy barrier.
The difficulty in answering this question lies in determining the time itself and how it is applied to the tunnel effect. In this new work, the researchers used a simplified approach to measuring how long it takes one type of particle (rubidium atom) to pass a very specific kind of energy barrier (laser beam). The “clock” in their experiments was the rotation of the used rubidium atoms. Since the duration of their rotation is a known quantity, they can be used as a clock, measuring how many rotations occur when particles pass through a barrier, in this case, a laser beam. Thus, all the researchers had to do was record the current spinning state of the atom before it hit the beam and then measure it again when it came out.
The plan involved capturing a cloud of rubidium atoms using a laser beam. And then, using the same laser beam, move the atoms into the path of another laser beam, and measure their rotation on either side of the second beam. To make it easier to measure the rotation of the atoms, the researchers first cooled the cloud strongly and then sent the particles through the energy barrier. The rotation measurement showed that tunneling took approximately 0.62 milliseconds.
In further research, the researchers would like to know more about the trajectory of atoms as they pass through the barrier.