Applied Physics

Tuning Rainbows

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Science  06 Aug 2010:
Vol. 329, Issue 5992, pp. 611
DOI: 10.1126/science.329.5992.611-c

Robust and fast, single photons are viewed as ideal carriers of quantum information for applications in secure communication (cryptography) and quantum computing. At the heart of these processes lie single-photon emitters, devices that would emit identical, indistinguishable photons and allow their interference and entanglement. Single atoms or ions are ideal emitters but do not lend themselves to easy manipulation or scale-up for practical application. Solid-state quantum dots alleviate these issues but suffer from the problem that no two dots are alike—the ladder of energy levels varies from one dot to the next, and so the output from an array resembles a pretty rainbow rather than a mundane yet useful single wavelength. Using a solid-state quantum dot array and a distribution of organic molecules embedded in a matrix, respectively, Patel et al. and Lettow et al. show that applying an electric field can render the colors of the emitted photons identical. In a different approach, Flagg et al. show that local strain surrounding quantum dots can be used to tune the emission. This suite of techniques should be invaluable in meeting the scale-up requirements for technological applications.

Nat. Photon. 4, 10.1038/nphoton.2010.161 (2010); Phys. Rev. Lett. 104, 123605; 137401 (2010).

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