An Atomic Force Microscopy study of buried InAs/GaAs quantum-dot single-photon sources

Conventional light sources emit a large number of photons in a wide angular range and are mainly used for illumination or imaging purposes. Technological advances have allowed the dimensions of the components of devices to be reduced to the nanometre scale, and intriguing quantum mechanical effects have come into play. We are now able to manipulate matter at the atomic level and generate single photons, the smallest constituents of light, on-demand. The ability to control light emission at its smallest level, the single photon, is technologically challenging but tremendously interesting. The next revolution in communication is expected to take place by implementing quantum devices where light-matter interaction is engineered such that information can be stored in single photons that circulate between optical cavities within a photonic network. Given their scalability and the possibility of on-chip integration, solid-state single-photon sources are expected to be the building blocks of these novel quantum architectures. If we can store information on a single photon level, we can transfer it at the speed of light with a guaranteed secure communication: any measurement by an unwanted observer will leave a trace that will be visible to the receiver, thus unveiling the steal of information. However, several challenges are still limiting the implementation of quantum information technology in everyday life: the emitted photons only preserve their properties over a very short time-scale, often requiring cryogenic-cooled emitters excited by external lasers, and networks where information can be efficiently stored and shared are still lacking.
In this project we will investigate how the presence of nanometre-scale emitters buried within a semiconductor slab affects the surface morphology and how this, in return, impacts the properties of the single photons emitted. The outcome of this work will represent a step forward in the understanding of the emission properties of quantum light sources, allowing to improve the quality and reliability of single-photon emission, essential for information technology applications, like quantum computing and cryptography.

Quantum technology is currently moving beyond fundamental research laboratories and breaking into industry. Many companies are, investing in single-photon technology (e.g. Hewlett-Packard, Toshiba, IDQuantique, PicoHarp, Excelitas, Micro Photon Devices, etc.), proving the importance and timeliness of investing in this area for leveraging impact. The main beneficiaries of the proposed research are to be found in society, through the training of researchers, the investigation of faster and secure communication schemes and in industry, via the development and implementation of quantum information protocols in devices. Concerning academical impact, we will build up collaborations between overseas and national laboratories by collaborating with leading institutions in the U.S.: we will start new research projects that researchers in the U.K. will benefit from, directly (researchers in my group at the University of Southampton will interact with researchers at NIST and at The George Washington University and with our industrial partner Asylum Research) and indirectly, through the dissemination at conferences and seminars taking place in the U.K. .