  Generation of local magnetic field at the nanoscale is desired for many
applications such as spin-qubit-based quantum memories. However, this is a
challenge due to the slow decay of static magnetic fields. Here, we demonstrate
photonic spin density (PSD) induced effective static magnetic field for an
ensemble of nitrogen-vacancy (NV) centers in bulk diamond. This locally induced
magnetic field is a result of coherent interaction between the optical
excitation and the NV centers. We demonstrate an optically induced spin
rotation on the Bloch sphere exceeding 10 degrees which has potential
applications in all optical coherent control of spin qubits.
