  Universal quantum computing with continuous variables requires non-Gaussian
resources, in addition to a Gaussian set of operations. A known resource
enabling universal quantum computation is the cubic phase state, a non-Gaussian
state whose experimental implementation has so far remained elusive. In this
paper, we introduce two Gaussian conversion protocols that allow for the
conversion of a non-Gaussian state that has been achieved experimentally,
namely the trisqueezed state [Sandbo Changet al., Phys. Rev. X10, 011011
(2020)],to a cubic phase state. The first protocol is deterministic and it
involves active (in-line) squeezing, achieving large fidelities that saturate
the bound for deterministic Gaussian protocols. The second protocol is
probabilistic and it involves an auxiliary squeezed state, thus removing the
necessity of in-line squeezing but still maintaining significant success
probabilities and fidelities even larger than for the deterministic case. The
success of these protocols provides strong evidence for using trisqueezed
states as resources for universal quantum computation.
