Coherent and efficient microwave-to-optical conversion using Rydberg atoms

Frequency interconversion between microwave and optical fields will be important in future quantum information networks for connecting superconducting qubits and optical photons. However, this conversion is a real challenge as... [ view full abstract ]

Frequency interconversion between microwave and optical fields will be important in future quantum information networks for connecting superconducting qubits and optical photons. However, this conversion is a real challenge as the visible and microwave bands are separated by several orders of magnitude in frequency. Prior to attempting the quantum state transfer between microwave and optical photons, finding a system that can achieve coherent, efficient, and broadband conversion is essential. Here we demonstrate microwave-to-optical conversion via near-resonant frequency mixing involving Rydberg energy levels [1]. In contrast to other physical systems being investigated, our scheme does not require high-finesse cavities, and allows free-space and broadband conversion due to the strong coupling of microwave fields to atomic transitions between Rydberg states. Moreover, using electromagnetically induced transparency strongly enhances the efficiency and the coherence of the non-linear mixing. We are able to demonstrate the phase coherence of the converted light field with the input microwave field. Our results are in good agreement with theoretical predictions based on an independent atom model, which indicates a reduced effect of interactions. 

In this presentation, I will introduce our results, and discuss the strategies that we have developed for reaching near-unit conversion efficiency, which include using collinear frequency mixing, three-photon electromagnetically induced transparency (EIT) [2], and improved energy levels chemes. 

[1] J. Han, T. Vogt, C. Gross, D. Jaksch, M. Kiffner, and W. Li, “Microwave-assisted Rydberg electromagnetically induced transparency,” Phys. Rev. Lett. 120, 093201 (2018).

[2] T. Vogt, C. Gross, T. F. Gallagher, and W. Li, “Coherent Microwave-to-Optical Conversion via Six-Wave Mixing in Rydberg Atoms,” Opt. Lett. 43, 1822 (2018).