  Coherent interactions between electromagnetic and matter waves lie at the
heart of quantum science and technology. However, the diffraction nature of
light has limited the scalability of many atom-light based quantum systems.
Here, we use the optical fields in a hollow-core photonic crystal fiber to
spatially split, reflect, and recombine a coherent superposition state of
free-falling 85Rb atoms to realize an inertia-sensitive atom interferometer.
The interferometer operates over a diffraction-free distance, and the contrasts
and phase shifts at different distances agree within one standard error. The
integration of phase coherent photonic and quantum systems here shows great
promise to advance the capability of atom interferometers in the field of
precision measurement and quantum sensing with miniature design of apparatus
and high efficiency of laser power consumption.
