Matter-wave interferometry with trapped ions

Quantum mechanics endows massive particles with wave-like properties that can be put to good use in sensing applications.  Matter-wave interferometers have been made using everything from electrons to bucky-balls, but precision sensing applications with matter waves have generally been restricted to neutral atoms, which can be produced in large numbers and controlled fairly well.  We have recently invented a way to use trapped atomic ions as a gyroscope (rotation sensor), where the high degree of control found in this system can be used to overcome the small numbers of particles involved in the interference.  This work may someday be used in navigation applications where GPS (another useful product of atomic physics!) is not available, such as underwater or in the event of severe space weather.