  Quantum non-Gaussian states are crucial for the fundamental understanding of
non-linear bosonic systems and simultaneously advanced applications in quantum
technologies. In many bosonic experiments the important quantum non-Gaussian
feature is the negativity of the Wigner function, a cornerstone for quantum
computation with bosons. Unfortunately, the negativities present in complex
quantum states are extremely vulnerable to the effects of decoherence, such as
energy loss, noise and dephasing, caused by the coupling to the environment,
which is an unavoidable part of any experimental implementation. An efficient
way to mitigate its effects is by adapting quantum states into more resilient
forms. We propose an optimal protection of superpositions of coherent states
against a sequence of asymmetric thermal lossy channels by suitable squeezing
operations.
