Sagnac Interferometry with Dressed Internal States
Abstract
This project will proof the feasibility of a trapped-atom gyroscope, which allows for high-sensitivity measurements of rotation by determining the Sagnac phase in an interferometer. Such a device will constitute a matter-wave analogue of the interferometric fiber-optic gyroscope with a promise to achieve superior performance as a rate sensor in an inertial navigation system. The scientific promise arises from the rest mass of atoms. While photons necessarily travel near the speed of light along an optical fiber, atoms with a comparable quantum mechanical wavelength are much slower due to their higher mass. This leads to higher sensitivity to the rate of rotation via the larger angle swept over a round-trip time. But on the technical side, atomic mass also comes with the disadvantage of stronger influences from vibrations, acceleration, and gravity, which alter the atomic velocity and may even prevent the closing of an interferometric loop. The development pushed forward in this project will therefore follow an approach that does not rely on ballistic motion of atoms inside the waveguide. Instead, the interferometer will be operated akin to an atomic clock, where magnetically trapped atoms are put into a quantum mechanical superposition of two internal states. Atoms are then transported with controlled speed in opposite directions around a closed loop while they stay fully confined in state-dependent traps. After completion of the loop in a programmed time, a measurement of quantum mechanical phase will indicate the differential orientation angle of the device. The technical implementation is based on atom chips, i.e. micro-fabricated devices that allow for magnetic trapping and control of ultra-cold atoms. In certain configurations, the magnetic field gradients arising from ac and dc electric currents in the chip structure generate so-called radio-frequency dressed potentials to form state-dependent, transportable atom traps in ring-shaped geometries. Together with timing elements borrowed from microwave atomic clock technology, this provides all the necessary ingredients to implement the envisioned scheme. The work programme ranges from the demonstration of the basic operating principle to the technical development of improved designs to decrease apparatus size and power, including the necessary microfabrication and electrical, radio-frequency, and microwave engineering. We will investigate methods to maintain quantum mechanical coherence of the interferometer, and quantify and mitigate sensitivity to external factors, such as temperature drifts and vibrations. Characterizations of the first devices of this kind will inform the later transformation into practical sensors.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 10, 2019
- Source ID
- W911NF1910125
Entities
People
- Thomas Fernholz
Organizations
- Army Contracting Command
- Defense Advanced Research Projects Agency
- University of Nottingham