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November 28, 2009

Micropillars With Quantum Dots for Firing Single Targeted Photons


Tiny towers, a hundred times thinner than a human hair, with special properties: such nanostructures are produced by the Department of Applied Physics at the University of Würzburg. (Image: Monika Emmerling / Adriana Wolf)

[from Nanowerk] What is special about the Würzburg quantum dot towers is that "with them it is possible to 'fire off' single photons in a targeted fashion. It is structural elements like these that are needed for the tap-proof transmission of data in the field of quantum cryptography," explains Würzburg physicist Stephan Reitzenstein.

Embedded in the center of the towers are some 100 quantum dots made from the semiconducting material indium gallium arsenide.


Non-resonant dot–cavity coupling and its potential for resonant single-quantum-dot spectroscopy

Non-resonant emitter–cavity coupling is a fascinating effect recently observed as unexpected pronounced cavity resonance emission even in strongly detuned single quantum dot–microcavity systems. This phenomenon indicates strong, complex light–matter interactions in these solid-state systems, and has major implications for single-photon sources and quantum information applications. We study non-resonant dot–cavity coupling of individual quantum dots in micropillars under resonant excitation, revealing a pronounced effect over positive and negative quantum dot mode detunings. Our results suggest a dominant role of phonon-mediated dephasing in dot–cavity coupling, giving a new perspective to the controversial discussions ongoing in the literature. Such enhanced insight is essential for various cavity-based quantum electrodynamic systems using emitters that experience phonon coupling, such as colour centres in diamond and colloidal nanocrystals11. Non-resonant coupling is demonstrated to be a versatile 'monitoring' tool for observing relevant quantum dot s-shell emission properties and background-free photon statistics.

5 pages of supplemental information



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