Identifying different mechanisms in the control of a nitrogen-vacancy center system

The nitrogen-vacancy (NV) center system has shown great potential in quantum computing due to its long decoherence time at room temperature by encoding the qubit in dressed states [28]. The corresponding control mechanisms, which is expressed by the pathways linking the initial and target states, can be naturally investigated with the Hamiltonian-encoding and observable-decoding (HE-OD) method in the interaction adiabatic representation. This is proved by the fact that the mechanisms change slightly with different detunings, magnetic and driving field intensities, and the dominant pathway is always |g〉→|d〉→|g〉, with |g〉 and |d〉 as the first two lowest dressed states. Cases are different in the diabatic representation. The orders of dominant pathways increase the driving field intensities. Tendencies of quantum pathway amplitudes with driving fields, magnetic fields and detunings change at different conditions, which can be analyzed from the Dyson series. HE-OD analysis show that the two states |g〉 and |d〉 in the interaction adiabatic representation are preferable to be employed as a qubit than the state pair |0〉 and |−1〉 in the diabatic representation under the current Hamiltonian and parameters.