Build-your-own optical cycling transitions

To probe the spin states of optically-active quantum emitters, researchers often use cycling transitions whereby an optical field couples a target ground state to an excited state that primarily decays back to the same ground state. In this way, if the emitter is in the target ground state, it can be excited multiple times, resulting in multiple opportunities to measure its state. This method has led to high-fidelity single-shot readout of spins in diamond color centers, including nitrogen vacancy and silicon vacancy centers. Certain physical systems, however, do not contain such cycling transitions. For example, when the magnetic field applied to the silicon vacancy center is misaligned from the defect’s axis (a requirement for coupling phonons to its spin), the cyclicity of its optical transitions is greatly suppressed. When the system is optically excited under these conditions, it may decay to an undesired ground state, dramatically reducing the fidelity of the optical readout. Here, we evaluate the possibility of an induced cycling transition, caused by the creation of coherence in the excited state manifold and designed such that undesired decay channels are suppressed.