  Even though Gaussian quantum states of multimode light are promising quantum
resources due to their scalability, non-Gaussianity is indispensable for
quantum technologies, in particular to reach quantum computational advantage.
However, embodying non-Gaussianity in a multimode Gaussian state remains a
challenge as controllable non-Gaussian operations are hard to implement in a
multimode scenario. Here, we report the first generation of non-Gaussian
quantum states of a multimode light field by subtracting a photon in a desired
mode from multimode Gaussian states, and observe negativity of the Wigner
function. For entangled Gaussian states, we observe that photon subtraction
makes non-Gaussianity spread among various entangled modes. In addition to
applications in quantum technologies, our results shed new light on
non-Gaussian multimode entanglement with particular emphasis on quantum
networks.
