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We show that a coherent superposition of coherent states remains highly nonclassical when it is amplified through a linear phase-sensitive or phase-insensitive amplifier. The nonclassicality persists for arbitrarily large gain. We also propose a scheme for the observation of quantum interference via phase-sensitive amplification. The basic idea is to amplify a Schrodinger-cat state through a phase-sensitive two-photon CEL amplifier such that there is no added noise in the quadrature of interest and all the noise is fed into the conjugate quadrature. This scheme allows us to avoid the problem of detector efficiency in balanced homodyne detection.