Non-classical optical sources emitting single photons are required for applications in quantum information science. Quantum cryptography, for instance, exploits the fundamental principles of quantum mechanics to provide unconditional security for communication. 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. The field of quantum photonics has seen a tremendous development in recent years, leading to major advances in the understanding and control of solid-state systems at the quantum level. Current technology allows the realization of nanophotonic structures containing quantum emitters that enable single photons to be emitted on demand. These are the building blocks of many quantum information protocols and very exciting prospects seem within reach. The development of quantum information technology is expected to have an impact on everyday life, providing secure communication and faster and more efficient computation schemes. 

This project is focused on the study of solid-state single-photon sources, like semiconductor quantum dots (see image), from a fundamental perspective and in view of applications. These nanostructures resemble artificial atoms for many of their properties, most importantly the three dimensional confinement of the carriers, that results in the discreteness of the energy levels and thus sharp emission lines, and they can be embedded in on-chip optical cavities and waveguides, to control their emission properties and the propagation of light.

The student will have access to the fabrication facilities of the £120M Nanofabrication Facility of the Mountbatten clean room (http://www.southampton-nanofab.com), where the photonic devices (optical cavities and waveguides) will be fabricated. She/he will get hands-on experience in near-infrared and visible spectroscopy for the optical characterisation of single-photon sources.
For more information, please visit our group website at http://www.quantum.soton.ac.uk and contact Dr Luca Sapienza (l.sapienza@soton.ac.uk).