  We report on the realization and verification of quantum entanglement between
an NV electron spin qubit and a telecom-band photonic qubit. First we generate
entanglement between the spin qubit and a 637 nm photonic time-bin qubit,
followed by photonic quantum frequency conversion that transfers the
entanglement to a 1588 nm photon. We characterize the resulting state by
correlation measurements in different bases and find a lower bound to the Bell
state fidelity of F = 0.77 +/- 0.03. This result presents an important step
towards extending quantum networks via optical fiber infrastructure.
