• Single-photon emission by solid-state nanostructures

Non-classical optical sources emitting single photons are required for applications in quantum information science. An essential element of secure key distribution in quantum cryptography is an optical source emitting pulses containing one and only one photon, a so-called triggered single-photon source. Since measurements unavoidably modify the state of a single quantum system, an eavesdropper cannot gather information about the secret key without being discovered, if the pulses used in transmission contain only one photon. One of the goals of quantum information technology is to securely store information in single photons and transmit it, at the speed of light in the medium, within an all-optical network. We will work on the optical characterization of the single-photon emission by solid-state nanostructures, under laser excitation, at cryogenic temperatures. The student will get hands-on experience on laser excitation, cryogenics and optical characterization of nanostructures, by carrying out photoluminescence experiments.

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  Simulation of electromagnetic wave propagation in nanostructures

Solid-state single-photon sources are one of the best candidates for the realization of scalable quantum information technology applications. They can be integrated on a chip, where light can be guided in waveguides and trapped in optical cavities, and these optical components can be realized making use of a well-established semiconductor fabrication technology. Optical cavities can allow the efficient vertical extraction of single photons that can then be optimally coupled into an optical fibre and transmitted over long distances. The student will design optical cavities and waveguides and study the propagation of electromagnetic waves in the structures, by using finite-difference methods. We will optimize the emission pattern of solid-state emitters and introduce novel designs for light trapping and guidance to enhance the light-matter interaction at the nanoscale.

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  Fabrication of nanophotonic devices for single-photon applications

Solid-state single-photon sources are one of the best candidates for the realization of scalable quantum information technology applications. They can be integrated on a chip, where light can be guided in waveguides and trapped in optical cavities, and these optical components can be realized making use of a well-established semiconductor fabrication technology. Optical cavities can allow the efficient vertical extraction of single photons that can then be optimally coupled into an optical fibre and transmitted over long distances. The student will acquire hands-on experience on the fabrication of nanoscale devices like optical cavities and waveguides. She/He will have access to the fabrication facilities of the £120M Mountbatten clean room, where the photonic devices will be fabricated. Techniques will include e-beam lithography, dry etching and scanning electron microscopy.

For more information please contact Dr Luca Sapienza, l.sapienza[AT]soton.ac.uk