PM: Cavity-based Atomic Gravimeter

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Applying the principles of quantum mechanics holds promise to make extremely precise measurements, beyond the capabilities of more traditional methods. However, unwanted interactions of the quantum measurement device with the environment negate the advantages of quantum measurement in a process known as decoherence. One particularly interesting class of quantum measurement devices are atom interferometers. To avoid unwanted decoherence, they are usually performed with particles in free fall, but the available height limits these setups to time scales below 3 seconds. This project builds on an alternative approach, suspending atoms in a laser beam that forms a periodic, attractive potential for the atoms. The aim is to realize coherences for as long as several minutes, and thereby realize the most sensitive atomic device to measure gravity. This will then be applied to fundamental research in gravitational physics. In addition, the research will have broader impacts in contributing to UC Berkeley's efforts to educate a "quantum workforce" by offering hands-on training to undergraduate and graduate students. The proposal builds on the previous demonstration of 20-second coherences in a lattice-hold atom interferometer using an optical lattice formed by a resonant laser beam inside an optical resonator. Based on the observation that lowering the atom temperatures strongly increases the coherence, longer coherence times will be achieved by upgrading the experiment with a Bose-Einstein condensed (BEC) atomic sample. The next step will be to test whether the strongly reduced atomic temperature will lead to minutes of coherence time and a sensitivity of up to 2 nano-g in one second of integration time (where g is the earth's acceleration of free fall), realizing the world’s most sensitive atomic gravimeter. If this is successful, it will form the basis for the proposed test of the gravitational Aharonov-Bohm effect, in which a miniaturized test mass will form a "w"-shaped gravitational potential. Atomic wave packets will be brought to two points at which the potential does not apply forces on the atoms, and the Aharonov-Bohm induced phase shift will be recorded. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.