Seminarium Optyczne

Rydberg tweezer arrays and trapped ions are leading platforms for quantum simulation and computing, but local manipulation and readout typically require auxiliary atoms in neighboring traps. We take a different route and encode two qubits in two individually controlled electrons of a single 88Sr atom: a microwave qubit encoded in a pair of circular Rydberg states and an optical qubit on the narrow quadrupole transition of the Sr+ ionic core. We show coherent control of the core qubit with coherence times of several hundred microseconds under dynamical decoupling. The electrostatic quadrupole interaction between the distant Rydberg electron and the core couples the two qubits coherently, with a strength we tune via the angle between the quantization axis and the Rydberg orbit. Based on this coupling, we realize a two-qubit rotation gate that passes through an entangled state. The result is a pair of individually addressable electronic qubits with tunable coupling, inside a single atom, with applications in quantum simulation and metrology.