text: An important property of the non-radiative transition between E and A is that it is stronger for m = ±1 and weaker for m = 0. This provides the basis a very useful manipulation strategy, which is called spin state initialisation (or optical spin-polarization). To understand the process, first consider an off-resonance excitation which has a higher frequency (typically 2.32 eV (532 nm)) than the frequencies of all transitions and thus lies in the vibronic bands for all transitions. By using a pulse of this wavelength, one can excite all spin states from A to E. An NV center in the ground state with m = 0 will be excited to the corresponding excited state with m = 0 due to the conservation of spin. Afterwards it decays back to its original state. For a ground state with m = ±1, the situation is different. After the excitation, it has a relatively high probability to decay into the intermediate state A by non-radiative transition and further into the ground state with m = 0. After many cycles, the state of the NV center (independently of whether it started in m = 0 or m = ±1) will end up in the m = 0 ground state. This process can be used to initialize the quantum state of a qubit for quantum information processing or quantum sensing.
  Sometimes the polarisability of the NV center is explained by the claim that the transition from E to the ground state with m = ±1 is small, compared to the transition to m = 0. However, it has been shown that the comparatively low decay probability for m = 0 states w.r.t. m = ±1 states into A  is enough to explain the polarization.