Figure 1
From: Generation of macroscopic Schrödinger cat state in diamond mechanical resonator
(a) Schematic of the hybrid system, where the NV electron spin (red row) is embedded in the DMR. L, w, and h 
represent the length, width, and height of the DMR, respectively. (b) Levels of Δ-type transition ground-state electronic spin NV center, consisting of the levels of |0〉 and |±1〉, where, two classical microwave fields with frequencies ω1 and ω2 induce the transitions |0〉 ↔ |±1〉 with Rabi frequencies G1 and G2, respectively. In addition, the transition |+1〉 ↔ |−1〉 is coupled to the strain field (the frequency ωm) with the coupling strength λ. Dgs is the zero-field splitting between the state |0〉 and the nearly degenerated states |±1〉 which can be split by Δp in a magnetic field. Δ1(2) are the detunings between the frequencies of the transition |0〉 ↔ |±1〉 and the frequencies of the microwave fields. (c) Level structure of the effective Λ-type transition structure. The transitions |±〉 ↔ |+1〉 are coupled to the displaced quantized fields with the coupling strengths λ1 and λ2, respectively. The energy spacing between energy levels |+〉 and |−〉 is 2ω.
