Towards atom interferometry with atoms around an optical nanofiber

Light-pulse atom interferometry was invented in the 1990s and it has become a precise tool for measuring inertial forces and testing fundamental laws of physics. Using laser-cooled atoms as the coherence source and photon-atom momentum transfer to split and combine matter waves, atom interferometers have been developed as mobile gravimeters for gravy surveys and inertial sensors for inertial navigation. As their sensitivity scales with the light-atom interaction time, compact atom interferometers usually require a physical size from a few centimeters to a meter to allow the atoms to free-fall and on-chip atom interferometers have not yet been reported. The development of atom interferometers lags behind other advanced quantum sensing techniques, such as atomic clocks and magnetometers, in terms of miniaturization and reliability in field conditions. Here, we propose a new type of atom interferometry technique using an evanescent wave from an optical nanofiber. As the waist of the optical nanofiber is thinner than the laser wavelength, the optical nanofiber will not only guide the laser beam but also produce a tight-confinement evanescent field. We will first use a two-color optical lattice from the evanescent field to trap the atom around the optical nanofiber, and then create the atomic superpositions by Bloch oscillation with a moving optical lattice. Recently, we have successfully fabricated optical nanofibers by tapering regular single mode fibers to a waist of 200 nm and waist length of 5 mm with a laser transmission of 97%. We simulated the optical trapping with the evanescent wave from an optical nanofiber and Bloch oscillation in the evanescent lattice. Now we are building a magneto-optical trap of Rb⁸⁷ atoms and loading them on the optical nanofiber.