Deterministic Generation of Multipartite-Entangled Microwave Photonic States*

Sources of entangled electromagnetic radiation are a key component for distributed quantum information processing, metrology, and the study of quantum many-body physics. Generation of multi-mode entangled states of radiation with a large entanglement length, that is neither probabilistic nor restricted to generate specific types of states, remains challenging. Here, we demonstrate a unique superconducting device able to deterministically generate a wide family of entangled states of microwave radiation such as cluster, GHZ, and W states [1]. We tomographically reconstruct all quantum many-body states entirely for up to N = 4 photonic modes and characterize states for larger N by considering the repetitive nature of the sequential emission process. We estimate that localizable entanglement persists over a distance of approximately ten photonic qubits.
[1] Besse et al., Realizing a deterministic source of multipartite-entangled photonic qubits. Nature Communications 11, 4877 (2020).