Multiexcitation subradiant states are crucial resources for high-capacity quantum storage. Exploiting the unique dissipation characteristics of giant atoms provides a powerful mechanism for preparing such highly protected states. In this paper, we investigate the generation of multiexcitation subradiant states in giant-atom–waveguide systems with separate, nested, and braided configurations, explicitly accounting for inevitable dissipation into nonwaveguide modes. We demonstrate that all three configurations can significantly surpass the normalized subradiant population limit of conventional small-atom arrays. Notably, at the critical phase of $\phi =\pi$, both the separate and nested configurations completely decouple from the waveguide, achieving a perfect normalized subradiant population of 1. By evaluating the sensitivity to phase-matching errors, we uncover distinct differences in system robustness. Specifically, the separate configuration exhibits exceptional stability against phase fluctuations, followed by the braided array, while the nested configuration demonstrates extreme fragility. Consequently, the separate giant-atom configuration emerges as a superior platform for realizing high-capacity and robust quantum memory.

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• Open quantum systems & decoherence
• Quantum optics
• Superradiance & subradiance