Precision atom interferometry with squeezed atomic states

Recent advances in atom optics and atom interferometry have enabled observation of atomic de Broglie wave interference when atomic wavepackets are separated by distances exceeding 50 cm and times of 2 seconds. With further refinements, these methods may lead to meter-scale superpositions. In addition to providing new tests of quantum mechanics, these methods allow inertial force sensors of unprecedented sensitivity. We will describe methods demonstrated and results obtained in a 10 m atomic fountain configuration, their implications for technological applications in geodesy, and their relevance to fundamental studies in gravitational physics. We will describe how entangled atomic ensembles can be used to obtain further performance gains, following our demonstration of 18 dB measurement noise reduction using spin-squeezed atomic states.