- Rotating Wave Approximation (RWA)
- Born Approximation

3. The initial radiation field density operator
commutes with the free Hamiltonian, and the reservoir is not

affected by the
interactions with the system

4. Markov Approximation:

All these 4 approximation is called Born-Markov
Approximation.

*-Source : Yoshihisa Yamamoto & Atac Imamoglu, Mesoscopic Quantum Optics*