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Nanoelectronics and Nanophotonics: Cooperation and Accentuation of Quantum Functionality and Lasing

Final Activity Report Summary - NANOELECTROPHOTONICS (Nanoelectronics and Nanophotonics: Cooperation and accentuation of quantum functionality and lasing)

Progressing the theoretical understanding of unconventional electronic and photonic properties of nanoscale systems and devices - this was the objective of the Marie Curie Excellence Team "Nanoelectrophotonics", led by Professor Henning Schomerus at Lancaster University, UK, which has completed its four-year work successfully in October 2009. The investigated systems encompass nanoscale quantum dots which harbour only a handful of electrons, quantum wires, microresonator lasers not much larger than the optical wavelength, and atoms trapped in optical fields. Being so small, these systems are sensitive to the peculiar quantum mechanical combination of discreteness (small number of individual particles) and uncertainty (probabilities described by wave functions).

While these systems all show a great promise for applications in computing, communication, sensing and switching, they also pose some difficult challenges, due to their sensitivity to exterior factors, details of their geometric features, and internal sources of noise including "quantum noise". Overcoming these challenges requires a profound theoretical understanding of dynamics, transport and noise in quantum systems. Challenges arise also because the quantum properties can differ drastically for some materials, such as in the recently discovered graphene (an atomically thin layer of carbon atoms), where electrons move like ultra-relativistic neutrinos and possess an additional intrinsic quantum degree of freedom called "pseudospin".

Composed of individuals of a broad national and professional background, the Marie-Curie excellence team set out to making inroads on these problems by developing new theoretical descriptions which were backed up by extensive numerical investigations. Besides methodical achievements, the work of the team also led to the identification of novel phenomena. Research highlights include:
* The characterisation of various contact, interface, and surface effects in graphene, which all modify the electronic transport. These works served to explain a number of previously puzzling experimental observations. The team also proposed a new transistor mechanism based on pseudospin.
* A detailed understanding of adverse effects of the environment on optically driven quantum dots and atom-optical systems, in particular concerning conditions allowing the re-entrance of coherent quantum behaviour.
* Improvement, by one order of magnitude in accuracy, of the simple ray optics picture in microresonators. This was done by accounting for interface curvature and the small size of the systems.
* A detailed understanding of quantum noise in optical microresonators.
* The development of accurate approximate solutions to quantum problems based on their simpler classical behaviour.
* The description of quantum transport in systems with specific geometric symmetries.

These results were widely disseminated in 30 scientific publications and more than 60 conference presentations, posters and seminars.