  The phase relation between quantum states represents an essential resource
for the storage and processing of quantum information. While quantum phases are
commonly controlled dynamically by tuning energetic interactions, utilizing
geometric phases that accumulate during cyclic evolution may offer superior
robustness to noise. To date, demonstrations of geometric phase control in
solid-state systems rely on microwave fields that have limited spatial
resolution. Here, we demonstrate an all-optical method based on stimulated
Raman adiabatic passage to accumulate a geometric phase, the Berry phase, in an
individual nitrogen-vacancy (NV) center in diamond. Using diffraction-limited
laser light, we guide the NV center's spin along loops on the Bloch sphere to
enclose arbitrary Berry phase and characterize these trajectories through
time-resolved state tomography. We investigate the limits of this control due
to loss of adiabiaticity and decoherence, as well as its robustness to noise
intentionally introduced into the experimental control parameters, finding its
resilience to be independent of the amount of Berry phase enclosed. These
techniques set the foundation for optical geometric manipulation in future
implementations of photonic networks of solid state qubits linked and
controlled by light.
