article published yes Aviv Karnieli author Offek Tziperman author Charles Roques-Carmes author e2e68fc9-6505-11ef-a541-eb4e72cc3e82 Shanhui Fan author Enhancing interactions in many-body quantum systems, while protecting them from environmental decoherence, is at the heart of many quantum technologies. Waveguide quantum electrodynamics is a promising platform for achieving this, as it hosts infinite-range interactions and decoherence-free subspaces of quantum emitters. However, as coherent interactions between emitters are typically washed out in the wavelength-spacing regime hosting decoherence-free states, coherent control over the latter becomes limited, and many-body Hamiltonians in this important regime remain out of reach. Here we show that by incorporating emitter arrays with nonlinear waveguides hosting parametric gain, we obtain a unique class of many-body interaction Hamiltonians with coupling strengths that increase with emitter spacing, and persist even for wavelength-spaced arrays. We then propose to use these Hamiltonians to coherently generate decoherence-free states directly from the ground state, using only global squeezing drives, without the need for local addressing of individual emitters. Interestingly, we find that the dynamics approaches a unitary evolution in the limit of weak intrawaveguide squeezing, and we discuss potential experimental realizations of this effect. Our results pave the way towards coherent control protocols in waveguide quantum electrodynamics, with applications including quantum computing, simulation, memory, and nonclassical light generation. American Physical Society 2025 eng 2643-1564 2405.2024110.1103/physrevresearch.7.l012014 71 yes Karnieli, Aviv, Offek Tziperman, Charles Roques-Carmes, and Shanhui Fan. “Decoherence-Free Many-Body Hamiltonians in Nonlinear Waveguide Quantum Electrodynamics.” <i>Physical Review Research</i>. American Physical Society , 2025. <a href="https://doi.org/10.1103/physrevresearch.7.l012014">https://doi.org/10.1103/physrevresearch.7.l012014</a>. Karnieli A, Tziperman O, Roques-Carmes C, Fan S. 2025. Decoherence-free many-body Hamiltonians in nonlinear waveguide quantum electrodynamics. Physical Review Research. 7(1), L012014. Karnieli A, Tziperman O, Roques-Carmes C, Fan S. Decoherence-free many-body Hamiltonians in nonlinear waveguide quantum electrodynamics. <i>Physical Review Research</i>. 2025;7(1). doi:<a href="https://doi.org/10.1103/physrevresearch.7.l012014">10.1103/physrevresearch.7.l012014</a> Karnieli, A., Tziperman, O., Roques-Carmes, C., &#38; Fan, S. (2025). Decoherence-free many-body Hamiltonians in nonlinear waveguide quantum electrodynamics. <i>Physical Review Research</i>. American Physical Society . <a href="https://doi.org/10.1103/physrevresearch.7.l012014">https://doi.org/10.1103/physrevresearch.7.l012014</a> A. Karnieli, O. Tziperman, C. Roques-Carmes, and S. Fan, “Decoherence-free many-body Hamiltonians in nonlinear waveguide quantum electrodynamics,” <i>Physical Review Research</i>, vol. 7, no. 1. American Physical Society , 2025. A. Karnieli, O. Tziperman, C. Roques-Carmes, S. Fan, Physical Review Research 7 (2025). Karnieli, Aviv, et al. “Decoherence-Free Many-Body Hamiltonians in Nonlinear Waveguide Quantum Electrodynamics.” <i>Physical Review Research</i>, vol. 7, no. 1, L012014, American Physical Society , 2025, doi:<a href="https://doi.org/10.1103/physrevresearch.7.l012014">10.1103/physrevresearch.7.l012014</a>. 215612026-03-30T12:22:47Z2026-04-27T10:32:06Z