Verifying that 3-photon parametric down-conversion is a nonclassical resource

Nonlinear processes and non-Gaussian states are a critical resource for proposed continuous-variable quantum computation and quantum communication schemes. In early work, we demonstrated the generation of single-mode and multimode non-Gaussian states using a nonlinear three-photon down-conversion process in a flux-pumped superconducting parametric cavity. While we have generated correlated three-photon states with highly non-Gaussian statistics, key quantum properties such as negativity of the Wigner function and non-Gaussian entanglement have not been confirmed. Our work here aims to observe Wigner negativity of a tri-squeezed vacuum state generated by three-photon down-conversion into a single frequency mode of the cavity as a demonstration of this platform’s capabilities to generate nonclassical resource states. We will present preliminary results towards confirming the Wigner negativity of tri-squeezed states.