  State preparation via postselected weak measurement in three wave mixing
process is studied. Assuming the signal input mode prepared in a vacuum state,
coherent state or squeezed vacuum state, separately, while the idler input
prepared in weak coherent state and passing the medium characterized by the
second-order nonlinear susceptibility. It is shown that when the single photon
is detected at one of the output channels of idler beam's path, the signal
output channel is prepared in single-photon Fock state, single-photon-added
coherent state or single-photon-added squeezed vacuum state with very high
fidelity, depending upon the input signal states and related controllable
parameters. The properties including squeezing, signal amplification, second
order correlation and Wigner functions of the weak measurement based output
states are also investigated. Our scheme promising to provide alternate new
effective method for producing useful nonclassical states in quantum
information processing.
