Driving Rydberg-Rydberg Transitions from a Coplanar Microwave Waveguide

The coherent interaction between ensembles of helium Rydberg atoms and microwave fields in the vicinity of a solid-state coplanar waveguide is reported. Rydberg-Rydberg transitions, at frequencies between 25 and 38 GHz, have been studied for states with principal quantum numbers in the range 30–35 by selective electric-field ionization. An experimental apparatus cooled to 100 K was used to reduce effects of blackbody radiation. Inhomogeneous, stray electric fields emanating from the surface of the waveguide have been characterized in frequency- and time-resolved measurements and coherence times of the Rydberg atoms on the order of 250 ns have been determined. These results represent a key element in the development of an experimental architecture to interface Rydberg atoms with solid-state devices.

Figure 1

(a) Schematic diagram of the experimental apparatus (not to scale). (b) Photograph of the PCB containing the coplanar microwave waveguide.

Figure 2

Stark map of singlet He Rydberg states in the vicinity of $n=32$.

Figure 3

Microwave spectra of singlet $np\to ns$ transitions, in the range $n=31–35$, for He atoms traversing the coplanar waveguide. Simulated line shapes (red) are overlaid on the experimental data with the zero-field transition frequencies, ${\nu }_{\mathrm{zf}}$, indicated by arrows.

Figure 4

(a) Spectra of the singlet $33p\to 33s$ transition in He as a function of microwave power. The output power of the microwave source, $P_{\mu }$, is indicated on the right-hand side of each spectrum. (b) Dependence of the measured linewidth on $P_{\mu }$.

Figure 5

Fraction of Rydberg atoms in the $33s$ state as a function of microwave pulse duration for output powers of the microwave source of (a) $4\mu \mathrm{W}$ and (b) $10\mu \mathrm{W}$. The solid black lines are the results of numerical simulations.