CAREER: Atom Interferometry Experiments in Fundamental Physics

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Research supported by this CAREER award is exploring new ways to use atom interferometry to perform precision tests of fundamental laws of physics. An atom interferometer uses the wave-particle duality of quantum mechanics. An atomic (e.g., cesium) matter wave is split and sent along two paths. When the two waves are interfered, the probability of detecting the atom is given by the phase difference of the matter waves. The high sensitivity of atom interferometers derives from the fact that the phase difference can be millions of radians, whereas tiny fractions of radians lead to a measurable change in the detection probability. The instruments being constructed for this research use cesium and lithium atoms. They use "large momentum transfer," a new method that allows attaining a large separation of the matter wave's paths, thus increasing sensitivity. This method is further improved as part of this research.The instruments are applied to pursue an exciting research agenda in fundamental physics: Measuring a fundamental constant that characterizes the strength of the electromagnetic interaction, known as the fine structure constant, and thereby testing the theory of quantum electrodynamics to high precision; testing the notion that the force of gravitation must obey the laws of Einstein's theory of General Relativity, such as the fact that gravity knows no preferred direction; and testing the universality of free fall, one of the fundamental ingredients of the Einstein Equivalence Principle, from which all of General Relativity follows. Undergraduate students, graduate students, and postdocs take part, so this research helps training the next generation of scientists and engineers. The PI has noted that deep involvement in research often starts at a rather late stage of the student's career. The PI therefore seeks to increase the participation of undergraduate students, and in fact one of the interferometers used for this research has been set up mainly by an undergraduate student.