  We analyze truncation of coherent states up to a single-photon Fock state by
applying linear quantum scissors, utilizing the projection synthesis in a
linear optical system, and nonlinear quantum scissors, implemented by
periodically driven cavity with a Kerr medium. Dissipation effects on optical
truncation are studied in the Langevin and master equation approaches. Formulas
for the fidelity of lossy quantum scissors are found.
