Testing Theories of Dark Energy Using Atom Interferometry

Cosmological observations provide compelling evidence that the standard models of particle physics and cosmology are incomplete. Key observations are the presence and structure of the cosmic microwave background and the expansion history of the universe seen using Type 1a supernovae. These observations show that the expansion of the universe began to accelerate at the time of the formation of the solar system. The as-yet unknown cause of this expansion has been dubbed 'dark energy'. Dark energy is not explained in any current theory of physics or cosmology. Current observations are a poor guide to the structure and energy scales of the new physics needed. We propose to address these fundamental cosmological mysteries by making an improved search for dark energy using atom interferometry. In an atom interferometer a tiny sample of atoms in vacuum is cooled to nearly absolute zero. At such low temperatures an atom's quantum interaction with laser light makes it exquisitely sensitive to tiny forces such as one which might have its origin from dark energy. The improvements we will make will advance not only the search for dark energy but also the sensitivity of atom interferometers for detecting other new physics.