motion and collision of room-temperature atoms are apparently harmful [@nPhys_msmemory; @collision_JWPan], and therefore were avoided in purpose in previous endeavors of observing large-scale entanglement. Though being more challenging, it would be more desirable to explore whether large-scale entanglement can exist in ambient condition and shared by many more motional atoms, not only for the fundamental interest of probing the boundary of quantum to classical transition, but also for future real-life quantum technologies.

Here, we experimentally demonstrate a multipartite entanglement of billions of motional atoms in a quantum memory operated at room temperature. The multipartite entanglement W state in a hot atomic vapor cell is heralded by registering a Stokes photon through far off-resonance spontaneous Raman scattering (SRS). In order to certify and quantify the entanglement scale, we convert the shared excitation of W state into an anti-Stokes photon by applying another interrogation pulse, and reveal a entanglement depth up to billions of atoms by the witness constructed with the correlated photon statistics. The far off-resonance configuration endorses the broadband feature of our scheme allowing to be operated at a high data rate. Furthermore, our heralded and quantum memory built-in fashion of entanglement generation allows us to directly observe the dynamic 