Developing trapped ion technology for inertial sensing
Abstract
Gyroscopes based on atom interferometry have long held promise of greater absolute stabilitycompared to their solid state and optical counterparts by leveraging the universal properties ofatoms. With atomic beam gyroscopes there has been a tradeoff ~ in order to get a large enclosedarea to increase their sensitivity to rotations, the devices must be large (meter scale). On theother hand, optical interferometers have been made compact without sacrificing sensitivity bypassing light through thousands of loops of optical fiber to increase the enclosed area.We introduce a new technique that combines the advantages of both technologies ~ a trapped ionSagnac interferometer. Trapping is analogous to an optical fiber for ions, allowing potentiallythousands of orbits to accumulate the area enclosed by the interferometer. By using a harmonictrap, we also avoid the velocity-dependent sensitivity in typical atomic gyroscopes. We projectthat by combining demonstrated technologies, a trapped ion gyroscope with a random walk errorof 0.0048 degrees per root hr is feasible. In addition, techniques for preparing high-qualityentangled quantum states borrowed from quantum information processing furnish this newtechnology with a route to sub-shot noise sensitivity.We will create a single-ion Sagnac interferometer by first placing the ion in a superposition oftwo wavepackets taking oppositely directed orbits around the trap center. This superposition willbe created using demonstrated technology originally developed for ultrafast quantum computingknown as ~spin dependent kicks~ (SDKs), which map the ion~s qubit state to a superposition ofits external momentum states. This will be followed by a displacement of the ion from the trapcenter using trap electrodes to create the desired coherent superposition of orbits. If the ion trapitself rotates as the wavepackets orbit, the Sagnac effect will lead to a phase difference that wewill measure after reversing these displacements to recombine the wavepackets.The unique regime in which this interferometer operates endows it with some intriguingproperties. The sensitivity to rotation in our anticipated operating regime should be larger than asingle spin gyroscope by a factor of the ratio of their angular momenta, where the ion~s orbitalangular momentum in the trap is roughly 350,000 hbar. Since the Lorentz force from a static Bfieldis equivalent in form to the Coriolis force, an applied field can be applied to maintain fullinterference contrast and fringe phase independent of rotation rate, a technique we refer to as the~magnetic gimbal.~ Feedback of the fringe signal to the coils applying the field closes the loop,and the coil current becomes the gyroscope signal, thereby providing potential for a widedynamic range of measurement timescales and rotation rates with no loss of contrast.Furthermore, since the magnetic moment of the orbit is suppressed compared to an electron by afactor of the ratio of the electron mass to the mass of a 171Yb+ ion, the magnetic field sensitivityassociated with this effective spin-350,000 system is only about 1 Bohr magneton.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 03, 2017
- Source ID
- N000141712256
Entities
People
- Paul Hamilton
Organizations
- Office of Naval Research
- United States Navy
- University of California, Los Angeles