By Ugur Meric Gür
With the growing interest in quantum information technology, nanophotonic circuits are increasingly attracting the researchers’ attention. A major driver of the current research into single-photon sources
(SPSs), and also single-photon detectors, is the explosive growth of the field of quantum-information science over the last few decades. Quantum cryptography has been a significant driver of single-photon source development. SPSs are indispensable not only for photonic quantum circuits, photonic quantum simulators, and quantum key distribution, but also for innovations in the fields of quantum enhanced sensing and metrology. The challenges that must be overcome for these sources strongly depend on the targeted applications.
The field has reached a certain level of maturity. Today, it is possible to find nearly ideal devices when only one parameter is important, but performance of other parameters is often compromised. Specifically for sources, while initial efforts were focused mostly on increasing brightness and generation efficiency, current improvement efforts are more driven by the requirements for particular applications and often deal directly with improving more than one characteristic simultaneously, as it is now well understood that heroic results in improving a single parameter are often of little practical use. These multi-parameter efforts include better single-photon state accuracy and higher degree of indistinguishability of single-photon output states which is particularly important for many quantum-information applications.
Quantum dots (QDs) are a specific example of single-photon sources and belong to the class of deterministic sources. When single-photon emission is desired, some external control is used to put the system into an excited state that will emit a single photon upon relaxation to some lower-energy state.
While this is quite well mastered, the problem occurs in the collection and efficient light extraction, which poses a major challenge in the design of SPSs and it can be said that development of SPSs is still one of the biggest challenges in quantum communication.
The project will focus on the particular problem of collection efficiency and light extraction, but is not limited to it. Microwave and antenna techniques will be combined with the photonics approaches to analyze and improve the SPSs.
To be completed: 2021