Intertwining Electron Tunneling with Light

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Science  11 May 2012:
Vol. 336, Issue 6082, pp. 679-680
DOI: 10.1126/science.1221416

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If we try to lob a ball over a building but throw it too slowly, it bounces off. But a quantum-mechanical “ball” (e.g., an electron) also has a wave nature, and thus has a finite chance of tunneling through the barrier (as if our classical ball disappeared into the building and came out the other side). Quantum tunneling underlies natural processes such as radioactive decay and is harnessed in the operation of many devices, such as tunnel junctions and scanning tunneling microscopes. In these applications, tunneling rates are controlled by changing the barrier height or width, either by altering the design (e.g., changing the thickness of an insulating layer) or by applying an external electric field. In a study reported on page 704 of this issue, Cristofolini et al. (1) controlled electron tunneling optically by entangling the electron into a complex quasiparticle—which they call a “dipolariton”—partially made of light. This result opens up a wide range of optoelectronic applications based on coherent transfer between a photon state and an electron tunneling state.