Microwave saturation and the Rabi frequency of the Rydberg states of electrons on helium

We present measurements of the resonant microwave excitation of the Rydberg energy levels of surface state electrons on superfluid helium. The temperature dependent line width γ(T) agrees well with theoretical predictions and is very small below View the MathML source. Absorption saturation and power broadening were observed as the fraction of electrons in the first excited state was increased to 0.49, close to the thermal excitation limit of 0.5. The Rabi frequency was determined as a function of microwave power. The experiments show that the conditions are met for the use of these states in an electronic qubit.