Particles That Tunnel Together, Stay Together

Researchers have theoretically shown that in certain conditions, two particles will begin to act as if they are one molecule and undergo quantum tunneling together.

AsianScientist (Jun. 21, 2016) – A team of researchers in Japan has developed a technique to control two particles, rather than just one, by using quantum tunneling.

The research team at Okinawa Institute of Science and Technology Graduate University (OIST) has theoretically shown that it is possible to reliably transport both particles completely through barriers. The study findings are published in Physical Review A.

In quantum mechanics, physicists study tiny single particles—photons and electrons—and usually only a small number of them at a time. Sometimes, these particles behave like waves, which gives them very unique properties that can be manipulated or controlled.

The wave-like particles considered by the researchers are contained in ‘traps’ that can be created with light or magnetic fields. In order to move a particle from one trap to another, the traps need to be brought close together to make the walls between them thinner. When this happens, a phenomenon called tunneling occurs, allowing the particle to ‘move’ through the walls and from one trap to the other.

However, this does not happen all at once and the particle can begin to tunnel back and forth, making it very difficult to get the entire particle through the wall and into a different trap.

Physicists have overcome this by a series of steps. First, they added two additional traps to the right of the trap containing the particle. Then, one by one, they moved the farthest right trap and then the farthest left trap closer to the middle trap. This way, a single particle can be fully transferred to the rightmost trap with very high reliability.

While this process works perfectly for one particle, it becomes exponentially more difficult trying to do it for two particles because the particles interact and repel each other.

Despite the increased complexity, the OIST researchers found to their surprise that for a large range of interactions both particles were simultaneously transported to another trap, using the same method as described above.

“You would think that because the particles are repelling each other they would not want to stay together, but what we see here is that they are able to move through the traps because at some point they begin to act as if they are one molecule instead of two particles, and tunnel together,” said OIST post-doctoral scholar Dr. Albert Benseny, the first author of the study.

The researchers are now finding the interaction regions at which this process works robustly, a pre-requisite for advances in quantum technologies—particularly quantum computing—where processes must work with 99.99 percent certainty.

The article can be found at: Benseny et al. (2016) Spatial Adiabatic Passage via Interaction-induced Band Separation.


Source: Okinawa Institute of Science and Technology Graduate University .
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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