Bloch oscillations with a metastable helium Bose-Einstein condensate

We have observed Bloch oscillations of a 4He∗ Bose-Einstein condensate in an optical lattice at 1557.3 nm. Due to its low mass, metastable helium was efficiently accelerated orders of magnitude faster than demonstrated with other atoms. In a horizontal lattice, we could transfer a total of 800ℏk of momentum by shuttling the atomic cloud back and forth 50 times between the 4 k and -4 k momentum states with an efficiency of over 99% per Bloch cycle. In a vertical lattice, gravity-induced Bloch oscillations were demonstrated, from which the local gravitational acceleration was derived with a statistical uncertainty of 4×10-5. A clear advantage of He∗ over other atoms is that it can be detected with a microchannel plate detector with near unity efficiency, and this enabled observation of Bloch oscillations up to 12 s even though the number of atoms decreased by three orders of magnitude. These results establish He∗ as a promising candidate for future precision measurements with atom interferometry.