Generating and characterizing generalized squeezed states in a superconducting microwave cavity

Continuous-variable quantum information processing necessitates the generation and manipulation of non-Gaussian photonic states, such as higher-order generalized squeezed states and cubic phase states. These non-Gaussian states are distinguished from conventional Gaussian states by their pronounced Wigner negativity in phase space. However, generating these states with large Wigner negativity remains experimentally challenging, hindering their practical applications. Here, we experimentally generate non-Gaussian generalized microwave squeezed states (including tri- and quad-squeezed states) and cubic phase states within a high-quality superconducting cavity. This is achieved by engineering generalized photon-number filter operations in a programmable parameterized quantum circuit that efficiently projects cavity states onto target non-Gaussian states. These generalized squeezed photonic states are demonstrated to exhibit large Wigner negativity and quantum Fisher information as the squeezing order and squeezing parameter increase, thereby confirming their non-Gaussianity and highlighting potential applications in continuous-variable quantum information processing and quantum metrology.