Atom Interferometry

Physics: Mach-Zehnder atom interferometer: π/2 pulse (beam splitter) creates superposition, π pulse (mirror) redirects, π/2 pulse (recombiner) creates interference. Gravitational phase: Δφ_g = k_eff·g·T² where k_eff = 2k_laser (two-photon Raman transition). Sensitivity to g: Δg/g ~ 10⁻⁹ (exceeds optical gravimeters). Sagnac phase for rotation: Δφ_Ω = 4mΩA/ℏ where A is enclosed area. de Broglie wavelength λ_dB = h/(mv) ~ 10 pm for Rb at 1 m/s. Applications: inertial navigation, geodesy, tests of equivalence principle (WEP), gravitational wave detection. Kasevich & Chu 1991 first demonstration.