Quantum reflection of antihydrogen from a liquid helium bulk

We study the quantum reflection of ultracold antihydrogen atoms bouncing on the surface of a liquid helium bulk. The Casimir-Polder potential and quantum reflection are calculated and compared to the same quantities for other bulks. Antihydrogen can be protected from annihilation for as long as 1.3 s on a bulk of liquid 4 He, and 1.7 s for liquid 3 He. These large lifetimes open interesting perspectives for spectroscopic measurements of the free fall acceleration of antihydrogen.