Quantum optics truncated states

We can treat FD quantum-optical states as those of a real single-mode electromagnetic field, which fulfill the condition of truncated Fock expansion. These states can directly be generated by the truncation schemes (the quantum scissors) proposed by Pegg et al. [44] and then generalized by other authors [45-47]. Alternatively, one can analyze states obtained by a direct truncation of operators rather then of their Fock expansion. Such an operator truncation scheme, proposed by Leonski et al. [48-50], will be discussed in detail in the next chapter [51]. 

---