Ultrafast lasers and trapped ions

Short, high-intensity laser pulses can be used to drive fast quantum logic gates between trapped ions. A high degree of control over the pulses properties is necessary for high-fidelity gates. We demonstrated reliable excitation of a single barium ion on a sub-femtosecond time scale. The next step is to perform a phase gate on a single ion by driving this excitation spin-dependently.

Our tools are modelocked lasers producing trains of short (fs to ps) pulses at about 100 MHz rep rate. Since these lasers are typically based on Ti:Sapphire crystals, their emission is in the near-infrared and needs to be frequency-doubled to drive the dipole-allowed transitions in Ba⁺ . Another option which has its advantages is to use the 1762 nm quadrupole-allowed transition instead. We plan to develop a stable ultrafast laser source at this wavelength.