Cavity quantum electrodynamics with a single silicon-vacancy center in diamonds and an ultrahigh-Q toroidal microcavity

• Applicant: Professor Dr. Sungkun Hong
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 551380071

Developing high-cooperativity cavity quantum electrodynamics (CQED) systems with long-lived quantum memory is a significant subject in quantum science, as it can enable numerous outstanding quantum technologies. Despite recent advancements, high-cooperativity CQED systems have only been realized under limited circumstances. In this research, we aim to develop a novel CQED system that exhibits strong cooperativity well above unity in the unexplored ‘good cavity’ regime. We will realize this goal by developing a hybrid CQED system that consists of a single silicon-vacancy (SiV) center in nanodiamond and a microtoroid optical cavity with an ultrahigh quality factor. The idea is based on our findings that a significant coupling can be achieved when a SiV-containing nanodiamond is placed on the surface of a silica microtoroid cavity. While the coupling may not be as strong as the current state-of-the-art, we find that the Q factor of our cavity outperforms the existing system by several orders of magnitude, thus resulting in similarly high cooperativity. Moreover, the ultrahigh Q factor of our cavity places our CQED system in an unexplored parameter space of a ‘good cavity’ regime. To realize this idea, we combine our complementary expertise in ultrahigh-Q cavity development (KPI) and low-temperature photoluminescence (PL) experiments (GPI). The research program is designed to utilize the expertise of both PIs maximally: while the KPI will focus on optimizing and further improving the performance of the microtoroid devices, the GPI will aim to build the low-temperature PL setup and use it to measure and verify the cooperativity of the resulting system. We expect our research will have a significant impact on the broad field of quantum science and technology. The realization of high-cooperativity QED systems will enable numerous applications in quantum communication and computing. Moreover, our system will constitute the first system in the so-called ‘good cavity’ regime. It thus can trigger new findings and technological innovation within and outside this research field, which can further impact our society in broader contexts. We also emphasize that this collaborative research will not only strengthen the partnership between the PIs but also create new research networks within and outside the host institutions, which will impact the collaborative research landscape between the two countries in the long term.

• DFG Programme: Research Grants
• International Connection: South Korea
• Major Instrumentation: Closed-cycle 4K cryostat ; Narrow-linewidth tunable laser
• Instrumentation Group: 5700 Festkörper-Laser ; 8550 Spezielle Kryostaten (für tiefste Temperaturen)
• Cooperation Partner: Professor Hansuek Lee, Ph.D.