Hello,

We noticed you're browsing in private or incognito mode.

To continue reading this article, please exit incognito mode or log in.

Not an Insider? Subscribe now for unlimited access to online articles.

Emerging Technology from the arXiv

A View from Emerging Technology from the arXiv

Physicists propose new kind of quantum tunneling

Quantum tunnelling of a new, third kind could finally put string theory to the test

  • April 20, 2009

Tunneling is the weird and wonderful process by which a quantum particle passes through a potential barrier that a classical particle could not traverse. It comes about because of the Heisenberg uncertainty principle which gives a finite probability for a quantum particle to cross a barrier of specific height and thickness.

In recent years, physicists have explored the possibility of a second type of tunneling which happens in an entirely different way. This relies on the idea that a quantum particle can change into another quantum particle and back again with a certain probability. The tunnelling occurs when the particle changes from one that interacts strongly with a barrier and so cannot pass though it, into a particle that does not interact with the barrier and so passes through with ease.

For example, quantum particles that change briefly into particles of dark matter should pass through barriers that should otherwise be impassable. This kind of “shining-a-light-through-a-wall” experiment is a serious contender in the search for dark matter.

Now Holger Gies from the Friedrich-Schiller-Universitat in Jena, Germany, and Joerg Jaeckel from Durham University in the UK, are proposing a third kind of tunnelling. In this case, a quantum particle changes into a pair of virtual particles which pass through the barrier and then change back again.

They give the example of photons changing into minicharged particles, particles with tiny fractional electronic charges which are predicted by some forms of string theory. These should pass through mirrors that would otherwise reflect photons, making it seem as if the photons had tunneled through the barrier (which in effect they had).

That’s an interesting and potentially important way of testing the predictions of string theory. And there aren’t too many of those around.

Ref: arxiv.org/abs/0904.0609: Tunneling of the 3rd kind

Become an MIT Technology Review Insider for in-depth analysis and unparalleled perspective.

Subscribe today
Want more award-winning journalism? Subscribe to Insider Online Only.
  • Insider Online Only {! insider.prices.online !}*

    {! insider.display.menuOptionsLabel !}

    Unlimited online access including articles and video, plus The Download with the top tech stories delivered daily to your inbox.

    See details+

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

/3
You've read of three free articles this month. for unlimited online access. You've read of three free articles this month. for unlimited online access. This is your last free article this month. for unlimited online access. You've read all your free articles this month. for unlimited online access. You've read of three free articles this month. for more, or for unlimited online access. for two more free articles, or for unlimited online access.