Imagine you are walking and encounter a barrier, such as a hill or a wall. The only way to make it to the other side is to climb all the way up and over it. Yet what if you had the same superpowers as quantum particles?
The strange laws of quantum mechanics allow particles to sometimes bust through barriers like they are not there, even if the particles cannot climb over whatever is in their path. But the challenge of tunneling through these barriers increases as the roadblocks get taller, making it so that fewer particles can break through. A special case of quantum tunneling called Klein tunneling, however, changes the game. It effectively makes barriers transparent, opening up portals that allow particles to pass through, even when incredibly tall walls stand in their way.
Nearly 100 years ago, Swedish physicist Oskar Klein first predicted this phenomenon. Yet until recently, scientists had seen very limited signs of it. In a study published in Nature on June 19, an interdisciplinary team of researchers present direct evidence of Klein tunneling.