Abstract
Chiral quantum optics is central to developing scalable quantum networks, yet existing approaches rely predominantly on linear single-photon regimes. It remains unclear how to generate directional multiphotons. Here we show that giant emitters coupled to nonlinear quantum optical baths enable tunable directional correlated photons, revealing a mechanism for multiphoton directional emission. We demonstrate that the propagation phases of correlated photons, together with the coupling phases of giant emitters, can generate destructive interference in one direction while enhancing emission in the opposite direction, making directionality fully tunable. Building on this mechanism, we introduce a nonlinear cascaded quantum network paradigm mediated by “correlated flying qubits”, providing a configurable building block enabling distinct many-body applications beyond linear unidirectional setups. These results reveal a rich landscape for engineering multiphoton propagation and correlations through interference in giant emitter-nonlinear bath architectures, offering pathways for quantum networks and strongly correlated light-matter platforms.
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Supplementary data for all the figures are provided at https://doi.org/10.5281/zenodo.18409019. Additional data that support the findings of this study are available from the authors upon request.
Code availability
The codes used for the simulation and analysis of the data are available from the authors upon request.
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Acknowledgements
X.W. is supported by the National Natural Science Foundation of China (NSFC) (Grant No. 12174303). Z.H.W. acknowledges the support from the National Natural Science Foundation of China (Grant No. 12375010). T.L. acknowledges the support from Guangdong Provincial Quantum Science Strategic Initiative (Grant No. GDZX2505004), National Natural Science Foundation of China (Grant No. 12274142), and the Introduced Innovative Team Project of Guangdong Pearl River Talents Program (Grant No. 2021ZT09Z109). A.F.K. acknowledges support from the Swedish Research Council (grant number 2019-03696), the Swedish Foundation for Strategic Research (grants numbers FFL21-0279 and FUS21-0063), the Horizon Europe program HORIZON-CL4-2022-QUANTUM-01-SGA via the project 101113946 OpenSuperQPlus100, and from the Knut and Alice Wallenberg Foundation through the Wallenberg Centre for Quantum Technology (WACQT). F.N. is supported in part by the Japan Science and Technology Agency (JST) [via the CREST Quantum Frontiers program Grant No. JPMJCR24I2, the Quantum Leap Flagship Program (Q-LEAP), the Moonshot R&D Grant Number JPMJMS256E, and the ASPIRE program (Grant Number JPMJAP2513).
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X.W. and T.L. conceived the original idea. J.Q.L. did the analytical and numerical analysis under the supervision of X.W. and T.L. Z.H.W., A.F.K., L.D., and F.N. provided very useful insights and guidance. All authors contributed to and approved the final version of the paper.
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Wang, X., Li, JQ., Wang, Z. et al. Nonlinear cascaded quantum network with giant emitters. Commun Phys (2026). https://doi.org/10.1038/s42005-026-02618-3
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DOI: https://doi.org/10.1038/s42005-026-02618-3
