The development of more stable and enhanced entangled-photon sources is crucial for large scale applications and will thrive on quantum technology like quantum networks, quantum telecommunication as well as quantum computing. Entangled-photon sources operating on demand satisfy the need of scaling up the complexity of the current quantum communication technologies. Therefore, epitaxial quantum dots have emerged as pioneers providing the requirements of emitting on demand highly indistinguishable single photons as well as polarization-entangled photon pairs with very high efficiency and fast repetition rate. Thus, giving rise to an emergent research field on quantum dots (QDs) focusing on improving the entanglement fidelity, photon indistinguishability and brightness to advance further towards the goal of establishing a vast quantum network.
To accelerate these new developments ground-breaking research especially on the single- and entangled-photon sources is a basic necessity. Understanding the phenomena degrading the photon indistinguishability and entanglement fidelity would allow for their compensation. Therefore, this project focuses on a novel investigation of the non-classical light emission, more accurately the single-photon purity and the entanglement fidelity, of GaAs/AlGaAs semiconductor QDs with respect to its excitation laser power. To holistically investigate the QD source both simulations on the statistical emission behaviour and an experimental examination is carried out. Therefore, exhibiting detailed information on the source and hence giving rise to a broad new research area.
Extensive fundamental studies and in-depth investigations on semiconductor QDs have led to a tremendous improvement in the understanding of these very versatile on-demand single- and entangled-photon sources [1]. Recent studies also focus on the emission properties as multi-photon emission probability [11] and entanglement effects [9] of semiconductor QDs. Even though these elementary studies are already providing good insight behaviours of semiconductor QDs, a holistic understanding is still not completely available. Thus, leading to experimentally observed below value results, as in terms of entanglement fidelity limiting its use in the vast application spectrum.
Our Nanophotonics Group under the supervision of Ass. Prof. Rinaldo Trotta at La Sapienza University has already developed a profound expertise on semiconductor QDs leading to outstanding results as the controlled cancelation of fine structure splitting stemming from fabrication imperfections [12] as well as the excellent achievements on entanglement fidelity of 98 % [8] and therefore, has greatly impacted the scientific community. Driven by our eagerness to improve our sources for real-life applications we want to gain better understanding on the performance, in particular the internal processes, and the consequent impact on the entanglement fidelity on the on-demand generated entangled pair of our semiconductor QDs. Therefore, we propose a thorough investigation on the entanglement fidelity with respect to excitation laser power.
We are confident that this research study will grant us key insights of the QDs operation performance, will give a comprehensive view on decoherence and dephasing mechanisms¿ in QDs with respect to excitation laser power and eventually give rise to mechanisms degrading the entanglement fidelity from its ideal 100 %. Our aim is to use this deeper understanding of the QDs operation to either systematically improve the QDs itself or develop post-growth correction techniques as are currently already effectively applied by our group for the controlled cancelation of fine structure splitting. We are convinced that this study will boost our knowledge on the performance of semiconductor QDs supporting the international community to realize quantum networks based on semiconductor QDs.