  Rydberg atoms are ideal tools for quantum technologies. Due to their large
size, their dipole-dipole interaction at micrometer-scale distances and their
coupling to external fields are huge. Recent experiments vividly exhibit their
interest for quantum simulation, in spite of limitations due to the relatively
short lifetime of optically-accessible Rydberg levels. These limitations
motivate a renewed interest for the long-lived circular Rydberg states .
However, detecting them is so far either destructive or complex. Moreover,
alkali circular states can be manipulated only by microwave fields, unable to
address individual atoms. Alkaline earth circular states, with their optically
active second valence electron, can circumvent these problems. Here we show how
to use the electrostatic coupling between the two valence electrons of
strontium to coherently manipulate a circular Rydberg state with optical
pulses. We also use this coupling to map the state of the Rydberg electron onto
that of the ionic core. This experiment opens the way to a state-selective
spatially-resolved non-destructive detection of the circular states and,
beyond, to the realization of a hybrid optical-microwave platform for quantum
technology.
