Optical manipulation of atomic motion for a compact gravitational sensor with a Bose-Einstein condensate interferometer.

摘要

Atom interferometers are among the best available devices for gravitational sensing. Standard devices, although unrivaled in sensitivity, cannot be made compact because they require the atom packets to be in free-fall over large distances on the order of one meter. In our experiments we create a novel type of interferometer as a proof-of-concept for a compact gravitometer. The limitation of a large drop distance is overcome by repeatedly applying a pulsed optical lattice to suspend two vertically separated packets of ultra-cold 87Rb atoms while keeping them in a state of virtual free fall.;To be competitive with the sensitivity of previous devices, many optical pulses will be required. An in-depth experimental and theoretical study of our pulses was performed. Previous methods could reflect the atomic motion with a theoretical maximum fidelity of 0.94, which would unacceptably limit the number of pulses that could be applied. This motivated the development of new high-fidelity manipulation pulses based on the idea of intensity pulse shaping. Several new pulse sequences of various orders were created and tested. Theoretical simulations predict fidelities that differ from unity by less than 1 part in 104 and experiment verified that fidelities are in fact greater than 0.99. With these pulses a single cloud of atoms was suspended against gravity for more than 120 ms by bouncing the atoms with 100 consecutive pulses. Previous bouncing experiments using other methods have only demonstrated a maximum of 3 bounces. Furthermore, this represents an unprecedented transfer of 200 single-photon momenta.;A vertically oriented atom interferometer using ultra-cold atoms was implemented, requiring only 10 microns of vertical drop distance. After multiple pulses, the packets are recombined and an interference signal is observed. 81 successive operations were applied for a total interferometer time of nearly 50 ms. This work marks the first time so many individual pulses have been used in an atom interferometer of any kind.