PRESERVATION OF NONCLASSICAL CHARACTER DURING THE AMPLIFICATION OF A SCHRODINGER CAT STATE

We examine the nonclassical property of a Schrodinger cat state, i.e., a superposition of two coherent states, when it is amplified by eithe r a phase-sensitive or a phase-insensitive amplifier. In both cases th e corresponding P representation remains nonpositive in some area of t he complex plane, for any amplification factor. The contribution to th e P function from these areas decreases exponentially with an amplific ation factor. With a phase-sensitive amplifier the onset of decay can be postponed to a larger amplification factor. Thus the nonclassical n ature of the field can be preserved under a wide range of conditions, in spite of the noise introduced in the amplification process.