Disappearance of squeezing in superposition states and its manifestation in the energy density

Abstract

We have classified the superposition of squeezed wavepackets into two kinds and studied their quadrature squeezing. We have shown that the squeezing and higher-order squeezing in the quadrature disappear for the states of the first kind. However, for the second kind, it is possible to achieve the maximum amount of squeezing by adjusting the parameters in the superposition. The absence of squeezing for the superposition states is explained based on the expectation value of the energy density. We find that the expectation value of energy density in quantum wavepackets that shows no squeezing is positive. The energy density in the decoherence dynamics of single and two-mode squeezed states is also carried out. Our further analysis shows that different types of squeezed states, including states which are not wavepackets, exhibit negative energy density.