Entanglement-ready photon sources at telecommunication wavelengths

• Applicant: Professor Dr. Fei Ding
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 454635269

Sources of entangled photons lie at the heart of photonic quantum information processing. But to date there have been few ways to produce them efficiently. Since the 1980s pairs of entangled photons have been made through the process of spontaneous parametric down conversion (SPDC). Unfortunately, there are several intrinsic disadvantages of these sources, such as the low brightness and the lack of electric injection for practical applications. Semiconductor QDs have a strong potential to address these problems, as they can produce high quality entangled photon pairs on demand. The community have recently made significant progress on QDs emitting at short wavelengths (< 1 μm), including the precise control on the infamous “fine structure splitting” (FSS) and the fibre-integration techniques. However, to build a much-sought-after quantum network, one may have to take advantage of the existing telecommunication infrastructure and the low-loss nature of fibers at the C-band and O-band. This is a big challenge for QD-based sources, as most of the telecom QDs developed to date exhibit ultra-large FSS (> 100 μeV), low brightness, broad linewidth and significant charge fluctuations. We aim to introduce new MBE growth techniques and to grow telecom QDs with high structural symmetry and uniformity. The ambitious goal is that the majority of QDs are “entanglement-ready”, i.e. their FSS are smaller than the lifetime-limited linewidths. These sources will be potentially compatible with the commercial dark fiber networks for quantum telecommunication studies. To this end, important integration technologies, such as waveguide-integration and fiber coupling, will be also investigated.

• DFG Programme: Research Grants