Ultrafast Interferometric Sensing of Atomic Motion over a Wide Dynamic Range
We report sensing of the motional state of an atomic ion using ultrafast momentum transfers from a pulsed laser to create an ion interferometer. We separate the atomic wavepacket in phase space, where interference with itself at a variety of points allows us to perform state tomography, giving a map of the atomic motional state. One important application is the measurement of an average phonon number in a harmonic oscillator. This works inside of, and far outside the Lamb-Dicke regime, where the motional wavepacket is not small compared to the wavelength of light performing the momentum transfer.