Schmidt-Kaler, Ferdinand

Spin-selective coherent light scattering from ion crystals

Ferdinand Schmidt-Kaler - QUANTUM, University Mainz, Germany

We study collective light scattering from linear crystals with up to twelve 40Ca+ ions, acting as coherent single photon emitters. Light-scattering is induced by two-photon laser excitation, starting from the S1/2 to D5/2 quadrupole transition at 729 nm in combination with laser excitation of the D5/2 to P3/2 dipole transition at 854 nm, followed by a decay back to S1/2 via a single photon emission near 393 nm. The scattered intensity is recorded in the far field, featuring the interference of emitted light fields of the entire crystal. We optimize the interference's visibility of coherent scattering by the chosen laser beam geometry and sub-Doppler cooling of the crystal. Furthermore, we demonstrate spin-dependent coherent scattering and unveil the time evolution of a previously encoded spin texture in a crystal employing the recorded dynamics of the spatial frequency components of the fringe pattern. This might be in future of interest to read out correlation patterns of qubits as the results of a quantum computation or quantum simulation run.

The figure shows a linear crystal of 6 ions on a camera, but in the far field, and featuring interference fringes.