Two Indistinguishable Electrons Interfere in an Electronic Device

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Science  01 Mar 2013:
Vol. 339, Issue 6123, pp. 1041-1042
DOI: 10.1126/science.1234199

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In quantum mechanics, particles can be prepared in entangled states, so that measurement of a property on one particle determines the outcome for the other, no matter how far apart the particles may be. This "spooky action at distance" was demonstrated first with photons (1). One goal of condensed-matter physics has been to replicate quantum optics experiments with electrons (2). For example, the Hong-Ou-Mandel (HOM) experiment (3) can determine if two photons are indistinguishable—meaning that they have the same wavelength and polarization, and that they can become entangled if they overlap during propagation, as can happen at a beam splitter (a semitransparent mirror; see the figure, panels A and B). An electronic device that could demonstrate indistinguishability of electrons would be useful for quantum computing applications. On page 1054 of this issue, Bocquillon et al. (4) demonstrate such an analog of the HOM experiment with two electrons, generated from two different single-electron sources, colliding in the equivalent of a beam splitter in a single device.