Room temperature quantum light sources based on two-dimensional hexagonal boron nitride for daylight quantum communication (DAYLIGHT QUANTA)

• Applicant: Professor Dr. Tobias Vogl
• 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 445275953

Efficient, electrically-excited quantum light sources that operate at room temperature and can be used for daylight quantum communication are highly sought after. Color centers in 2D hexagonal boron nitride (hBN) are a promising candidate to overcome common technical difficulties for such solid-state light sources. In previous work, we have integrated quantum emitters in hBN within dielectric cavities and predict that the quantum light source outperforms state-of-the-art decoy protocols for quantum key distribution. We have also developed processes to fabricate emitters of high quality reliably.Since the optical transition energies of color centers in hBN vary within the spectrum from the UV to NIR, we can choose a transition energy at a Fraunhofer line in the solar spectrum and filter around this line, therefore, this scheme allows us to operate a quantum communication system during daylight, which strongly enhances the data communication rate. The electrical excitation of quantum emitters in hBN so far was impossible, due to the insulating nature of the host crystal. We want to use a novel approach, where hBN hosting a single-photon emitter is placed on a tapered waveguide of a plasmonic tunnel junction. Tunneling electrons can excite surface plasmon polaritons which can travel to and subsequently excite the emitter. This scheme is compatible with on-demand single-photon generation by pulsing the tunnel current. We also need to fabricate emitters at pre-defined locations, e.g. at the waveguide tip. For this we will use localized radiation damage or strain-assisted defect formation, both of which we have developed already for random crystal sites. The electro-plasmonic excitation can be generalized and widely applied to other emitter systems and photonics with 2D materials in general. The quantum light source can be used in versatile scenarios, e.g. on a CubeSat for a global quantum internet.

• DFG Programme: Research Grants
• International Connection: Singapore, United Kingdom
• Co-Investigators: Dr. Falk Eilenberger; Professor Dr. Thomas Pertsch
• Cooperation Partners: Dr. Mete Atatüre; Professor Dr. Christian Nijhuis