Strong Collective Effects in Maser Oscillators

• Applicant: Dr. Christoph Zollitsch
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550083266

My project is aimed at advancing solid-state maser (Microwave Amplification by Stimulated Emission of Radiation) research by harnessing its inherent collective many particle effects. A large ensemble of emitters strongly coupled to a common resonator mode can give rise to a superradiance effect, where the individual emitters begin to synchronize. This results in a stronger emission as well as a more coherent emission, which spectrally corresponds to a large intensity and an ultra-narrow linewidth. I plan to enter this regime with a maser based on NV centers in diamond at room temperature. This will enable the experimental realization of a superradiant maser, featuring an ultra-narrow spectral linewidth, ideal for a microwave-based frequency standard or highly sensitive sensing. Further, by introducing a dissipative component to a system with strong collective effects, pathways for entanglement generation are possible. The strong collective interaction between a resonator and an ensemble of spins exhibits coherent Rabi oscillations between the resonator mode and a maximally entangled Dicke state in the spin ensemble. The Rabi oscillation prevents utilizing this entanglement. However, a dissipative interaction component can suppress the Rabi oscillations, leaving the system in a continuous state of entanglement, which can be accessed more readily. Finally, in my project I will lay the foundations for a real-world maser application by miniaturizing the bulky lab-based maser setup, into a handheld version. This will establish the maser as a versatile candidate for timekeeping, sensing and quantum technologies.

• DFG Programme: Research Grants