  The long-lived, efficient storage and retrieval of a qubit encoded on a
photon is an important ingredient for future quantum networks. Although systems
with intrinsically long coherence times have been demonstrated, the combination
with an efficient light-matter interface remains an outstanding challenge. In
fact, the coherence times of memories for photonic qubits are currently limited
to a few milliseconds. Here we report on a qubit memory based on a single atom
coupled to a high-finesse optical resonator. By mapping and remapping the qubit
between a basis used for light-matter interfacing and a basis which is less
susceptible to decoherence, a coherence time exceeding 100 ms has been measured
with a time-independant storage-and-retrieval efficiency of 22%. This
demonstrates the first photonic qubit memory with a coherence time that exceeds
the lower bound needed for teleporting qubits in a global quantum internet.
