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A team of researchers at the University of Toronto has found a way to measure how long the quantum tunnel takes to complete. In his article published in the magazine. NatureThe group describes the experiments they performed and the results they found when trying to measure how long the quantum tunnel takes under certain circumstances.
In a sense, quantum tunneling is simple: it is a phenomenon in which a particle passes through an energy barrier despite the lack of energy to do so. Scientists don’t really know how it works, but they’ve found it anyway, like making scanning tunnel microscopes. A factor in the quantum tunnel that has been debated by physicists for the past century is how long it takes for a particle to cross an energy barrier.
The difficulty in answering this question lies in defining time itself and how it applies to the quantum tunnel. In this new endeavor, the researchers took a simplified approach to measuring the time it takes for a type of particle (a rubidium atom) to pass through a very specific type of energy barrier (a laser beam). The “clock” in their experiments was the spin of the rubidium atoms used, since the duration of their spin is a known amount, they can be used as clocks by measuring how much spin occurs while being tested, such as going through a laser beam. Therefore, all the researchers had to do was observe the atom’s current spinning state before it entered the beam, and then measure it again when it exited.
Execution of the plan involved trapping a cloud of rubidium atoms using a laser beam and then using the same laser beam to move the atoms in the path of another laser beam, and measure their rotation on either side of the second beam. To make it easier to measure the spin of the atoms, the researchers first ultracooled the cloud before sending them through the energy barrier. Measurement of the change in turn showed that the tunnel took approximately 0.62 milliseconds.
In later research, researchers would like to learn more about the path of atoms as they move through the barrier, and they also point out that some theories have suggested that particles can move through a barrier without having passed through its interior.
Measuring the spin of a particle in a rapidly spinning object
Ramón Ramos et al. Measurement of the time spent by a tunnel atom within the barrier region. Nature (2020). DOI: 10.1038 / s41586-020-2490-7
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