Ultrafast Optics

Constraining the speed of tunneling

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Science  02 Jan 2015:
Vol. 347, Issue 6217, pp. 39-40
DOI: 10.1126/science.347.6217.39-f

In contrast to expectation and experience in the classical world, a particle in the quantum world hitting a barrier can appear on the other side, having tunneled through the otherwise impassible obstruction. Debate about how quickly tunneling occurs has existed almost since the discovery of quantum mechanics. Now, Landsman et al. use ultrafast optical techniques to measure the amount of time it takes to ionize a helium atom. By following an electron on attosecond time scales as it passes through the energy barrier and leaves the bonds of its parent atom, the authors rule out certain theoretical possibilities, thereby providing a clearer picture of the tunneling process.

Optica 1, 343 (2014); 10.1364/optica.1.000343 (2014).

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