GaSb/GaAs quantum rings as single photon sources

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Quantum technologies are those which exploit the exotic properties of nature described by quantum mechanics to deliverdevices with unprecedented speed or accuracy compared with conventional technology, or even generate completely noveltechnologies with new functionalities, which simply do not exist at present. Quantum cryptography is one such technology:communication whose security is guaranteed by fundamental laws of quantum mechanics. The implementation of quantumcryptography relies on the ability to generate single photons of light on demand. Several different physical systems havebeen used to generate single photons, but very few of them are suitable for commercial production as they are impracticaland inconvenient. An ideal single photon source should be fast, cheap, operate at room temperature, and emit photons atthe wavelengths used in existing optical-fibre based telecommunications systems. In fact, a practical single photon sourceis expected to look very like a type of semiconductor laser diode called a vertical cavity surface emitting laser (VCSEL). Inthis year-long project we will assess the feasibility of mass-producing low-cost, room-temperature single photon sourceswith telecom-wavelength emission by developing novel VCSEL devices whose active regions incorporate tinysemiconductor nanostructures called self-assembled quantum rings. This will allow us to leap-frog a stage in thedevelopment of practical, i.e. commercial, single photon sources, and to make a realistic assessment of their commercialpotential.