Non-Gaussian quantum states of a multimode light field

Advanced quantum technologies require scalable and controllable quantum resources 1 , 2 . Gaussian states of multimode light, such as squeezed states and cluster states, are scalable quantum systems 3 – 5 , which can be generated on demand. However, non-Gaussian features are indispensable in many quantum protocols, especially to reach a quantum computational advantage 6 . Embodying non-Gaussianity in a multimode quantum state remains a challenge as non-Gaussian operations generally cannot maintain coherence among multiple modes. Here, we generate non-Gaussian quantum states of a multimode light field by removing a single photon in a mode-selective manner from a Gaussian state 7 . To highlight the potential for continuous-variable quantum technologies, we first demonstrated the capability to generate negativity of the Wigner function in a controlled mode. Subsequently, we explored the interplay between non-Gaussianity and quantum entanglement and verify a theoretical prediction 8 about the propagation of non-Gaussianity along the nodes of photon-subtracted cluster states. Our results demonstrate large-scale non-Gaussianity with great flexibility along with an ensured compatibility with quantum information protocols. This range of features makes our approach ideal to explore the physics of non-Gaussian entanglement 9 , 10 and to develop quantum protocols, which range across quantum computing 11 , 12 , entanglement distillation 13 and quantum simulations 14 . Continuous-variables quantum information processing requires non-Gaussian states and operations. The generation of non-Gaussian quantum states of a multimode field is now reported through a mode-selective photon-subtraction scheme