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Quantum Dots for Quantum Information Technologies

Part of the series Nano-Optics and Nanophotonics pp 165-198

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The Mesoscopic Nature of Quantum Dots in Photon Emission

  • P. TighineanuAffiliated withThe Niels Bohr Institute, University of Copenhagen Email author 
  • , A. S. SørensenAffiliated withThe Niels Bohr Institute, University of Copenhagen
  • , S. StobbeAffiliated withThe Niels Bohr Institute, University of Copenhagen
  • , P. LodahlAffiliated withThe Niels Bohr Institute, University of Copenhagen

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Abstract

Semiconductor quantum dots share many properties with atoms such as discrete spectrum, which implies the ability to emit high purity single photons. However, they have unique features as well that are unknown to other emitters: they embody tens of thousands of atoms attaining large mesoscopic sizes, and lack the common atomic symmetries. Here we discuss two effects that are mediated by the mesoscopic nature and render quantum dots fundamentally different than atoms. The mesoscopic size and lack of parity symmetry causes the electric-dipole approximation to not be applicable to In(Ga)As quantum dots. As a consequence, the latter do not fulfil the atomic selection rules and thus interact with the electric and magnetic components of light on the same electronic transition. The multi-atomic nature also causes a collective mesoscopic effect in monolayer-fluctuation GaAs quantum dots, namely single-photon superradiance, giving rise to a giant light-matter coupling strength.