Amplification of higher-order squeezing

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Abstract
We examine the phase-insensitive amplification of three different kinds of higher-order squeezing. In particular, we consider fourth-order squeezing, intrinsic fourth-order squeezing, and amplitude-squared squeezing. It is found that for any input state both fourth-order squeezing and intrinsic fourth-order squeezing disappear at the output if the intensity gain is greater than 2. Amplitude-squared squeezing, on the other hand, can survive amplification at gains slightly greater than 2. Therefore the photon-cloning limit (intensity gain equals 2) is not a fundamental limit to nonclassical behavior.