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For a single particle, relaxation into different ground states is governed by fixed branching ratios determined by the transition matrix element and the environment. Here, we show that in many-body open quantum systems the occupation probability of one ground state can be boosted well beyond what is dictated by single-particle branching ratios. Despite the competition, interactions suppress all but the dominant decay transition, leading to a “winner takes all” dynamic where the system primarily settles into the dominant ground state. We prove that, in the presence of permutation symmetry, this problem is exactly solvable for any number of competing channels. Additionally, we develop an approximate model for the dynamics by mapping the evolution onto a fluid continuity equation, and analytically demonstrate that the dominant transition ratio converges to unity as a power law with increasing system size, for any branching ratios. This near-deterministic preparation of the dominant ground state has broad applicability. As an example, we discuss a protocol for molecular photoassociation where collective dynamics effectively acts as a catalyst, amplifying the yield in a specific final state. Our results open different avenues for many-body strategies in the preparation and control of quantum systems. Published by the American Physical Society2025 

Quantum sensing and metrology use coherent superposition states of quantum systems to detect and measure physical effects of interest. Their sensitivity is typically limited by the standard quantum limit, which bounds the achievable precision in measurements involving nominally identical but uncorrelated quantum systems. Fully quantum metrology involves entanglement in an array of quantum systems, enabling uncertainty reduction below the standard quantum limit. Although ultracold atoms have been widely used for applications such as atomic clocks or gravitational sensors, molecules show higher sensitivity to many interesting phenomena, including the existence of new, symmetry-violating forces mediated by massive particles. Recent advancements in molecular cooling, trapping and control techniques have enabled the use of molecules for quantum sensing and metrology. This Review describes these advancements and explores the potential of the rich internal structure and enhanced coupling strengths of molecules to probe fundamental physics and drive progress in the field.