Coherent Microwave-to-Optical Conversion via Six-Wave Mixing in Rydberg Atoms

Abstract

We present an experimental demonstration of converting a microwave field to an optical field via frequency mixing in a cloud of cold ^{87}Rb atoms, where the microwave field strongly couples to an electric dipole transition between Rydberg states. We show that the conversion allows the phase information of the microwave field to be coherently transferred to the optical field. With the current energy level scheme and experimental geometry, we achieve a photon-conversion efficiency of ∼0.3% at low microwave intensities and a broad conversion bandwidth of more than 4 MHz. Theoretical simulations agree well with the experimental data, and they indicate that near-unit efficiency is possible in future experiments.

Microwave-to-optical frequency conversion using a cesium atom coupled to a superconducting resonator

“…This indicates that two intervals is sufficient to obtain the majority of the performance. In contrast to previous works, which typically assume all Rabi frequencies are constant in time [30,31], we find that using time dependent pulses can greatly improve conversion efficiency. As a double-check and to employ a parametrization that is less discontinuous, we choose each envelope to be a Gaussian with a variable mean, amplitude, and width.…”

“…In these approaches the conversion is mediated by, respectively, a nano-mechanical resonator [7][8][9][23][24][25][26][27][28], an ensemble of trapped atoms [10,11,[29][30][31], and an ensemble of spins in a solid (e.g., NV-centers in diamond) [32][33][34][35][36]. A number of experiments have already demonstrated proof-ofprinciple conversion between microwaves and optical frequencies using a nano-mechanical system [25][26][27][28].…”

Coherent Conversion Between Microwave and Optical Photons—An Overview of Physical Implementations

“…Coherent fields at ω and Ω couple the transition at frequency . Reproduced with permission . Copyright 2018, APS.…”

“…Specific proposals have been made for caesium, rubidium, (Figure c,d) and ytterbium gases to be used, with several pumps coupling multiple transitions allowing an appropriate signal and output wavelength to be selected. Collective states in a gas of Rb have been strongly coupled to superconducting transmission line cavities and up‐conversion was first demonstrated using Rydberg states in Rb. Both of these experiments were carried out in the classical regime, with a significant thermal environment, and a maximum conversion efficiency of was demonstrated.…”

Microwave to optical photon conversion via fully concentrated rare-earth-ion crystals

“…Approaches using atoms [18,19] have been proposed. Recently, using the strong microwave and optical transitions of a cloud of Rydberg atoms at microkelvin temperatures, a conversion efficiency of 0.3% has been achieved with a 4 MHz bandwidth [20]. Collective spin excitations within a ferromagnet (magnons) have also been suggested.…”