Quantum theory does not prevent entanglement from being created and observed in macroscopic physical systems, in reality however, the accessible scale of entanglement is still very limited due to decoherence effects. Recently, entanglement has been observed among atoms from thousands to millions levels in extremely low-temperature and well isolated systems. Here, we create multipartite entanglement of billions of motional atoms in a quantum memory at room temperature and certify the genuine entanglement via M-separability witness associated with photon statistics. The information contained in a single photon is found strongly correlated with the excitation shared by the motional atoms, which intrinsically address the large system and therefore stimulate the multipartite entanglement. Remarkably, our heralded and quantum memory built-in entanglement generation allows us to directly observe the dynamic evolution of entanglement depth and further to reveal the effects of decoherence. Our results verify the existence of genuine multipartite entanglement among billions of motional atoms at ambient conditions, significantly extending the boundary of the accessible scale of entanglement.

量子理论并没有阻止在宏观物理系统中产生和观察纠缠，但实际上，由于退相干效应，纠缠的可及范围仍然非常有限。最近，在极低温和隔离良好的系统中，已经观察到原子之间从数千到数百万级的纠缠。在这里，我们在室温下在量子存储器中创建了数十亿个运动原子的多部分纠缠，并通过M证明真正的纠缠- 与光子统计相关的可分离性见证。发现单个光子中包含的信息与运动原子共享的激发密切相关，运动原子本质上是针对大系统的，因此刺激了多粒子纠缠。值得注意的是，我们的预兆和量子存储器内置纠缠生成使我们能够直接观察纠缠深度的动态演变，并进一步揭示退相干的影响。我们的结果证实了在环境条件下数十亿个运动原子之间存在真正的多部分纠缠，显着扩展了纠缠的可及尺度的边界。