Speaker
Description
The Bell test framework provides one of the clearest and most rigorous demonstrations of quantum nonlocality. While Bell non-locality tests have been extensively demonstrated with photons, experimental realisations with massive particles have been explored significantly less, due to the challenges with generating, manipulating, and independently measuring entangled matter-wave states. In this work, we demonstrate a violation of the Clauser–Horne–Shimony–Holt (CHSH) Bell inequality using momentum-entangled pairs of ultracold metastable helium atoms generated via spontaneous s-wave collisions between a Bose–Einstein condensates of metastable helium atoms. These collisions produce a double-halo scattering geometry that realizes a Bell state through a superposition of two indistinguishable pair-production pathways. To enable independent measurement settings for the two particles, we use a novel method involving a dual-resonant Bragg transition that imprints a different phase on two distinct momentum classes within the halo. This provides a coherent, independently tunable phase control of the spatially separated atoms. Using a Rarity-Tapster type matter-wave interferometer, we directly observe two-particle interference and measure a Bell parameter of S=2.52±0.17, demonstrating nonlocal correlations between atoms. This demonstration of non-locality with massive particles could be extended to investigate phenomena such as quantum gravity.
| I am the presenting author | Yes |
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