Optical Nanofiber Testbeds for Benchmarking Membrane-Waveguide Photonic Integrated Circuit Platforms toward On-Chip Quantum Inertial Sensing
Recent advances in cold atom interferometry with optical and magnetic atom guides have set the stage for quantum inertial sensors capable of operating in dynamic environments. In this work, we present three key innovations, such as evanescent-field (EF) atom guides, optical nanofiber testbeds, and membrane-waveguide photonic integrated circuit (PIC) platforms, to advance EF-guided atom interferometry. First, we demonstrate EF atom guides on optical nanofiber testbeds, which serve as performance benchmarks for our membrane-waveguide PIC platforms. Second, we achieve low-power (~5 mW) guiding of freely moving, laser-cooled 133Cs atoms in two-color, traveling-wave EF optical dipole traps at the novel, heat-efficient magic wavelengths of 793 nm and 937 nm (i.e. "793/937-nm EF atom guides"). We designed and fabricated membrane-waveguide PIC platforms for these EF atom guides; in our prior work we showed that they safely handle up to 4-6x times the minimum trap power under vacuum and enable dense cold atom generation for efficient loading. Third, we verify preserved atomic coherence via microwave fields and EF-coupled Doppler-free Raman beams; to our knowledge, this is the first report of coherence fringes driven by co-propagating EF-coupled Raman beams with only 150 nW of total optical power. By providing a direct comparison between optical nanofiber testbeds and membrane-waveguide PIC platforms, our results lay critical groundwork for the on-chip realization of EF-guided atom interferometry and the development of for fully integrated, low-SWaP (size, weight, and power) quantum accelerometers and gyroscopes.