High-power ultrafast laser source with 300 MHz repetition rate for trapped-ion quantum logic

Trapped ions are a major candidate technology for scalable quantum computation. However, current methods for performing quantum logic gates with trapped ions are limited to gate times of about 10 μs. This drawback was solved in a recently proposed scheme that uses pairs of counter-propagating π-pulses, resonant with an allowed ion transition, where the time needed for a gate operation is inversely proportional to the laser repetition rate. The MOPA architecture allows scaling to high repetition rate at constant pulse energy. In this paper, the authors designed a laser system to provide high-power picosecond pulses with a high repetition rate resonant with the 370 nm S-P transition in Yb+. The laser source is almost completely implemented in fibre, lending increased stability to the system. As ultrafast laser sources are not readily available at 370 nm, with sufficient optical power, pulses were prepared and amplified over a number of stages. A harmonically mode-locked Er-doped fibre (EDF) seed laser, with a repetition rate of 300 MHz and a wavelength of 1564 nm is amplified and compressed to form shorter femtosecond pulses at high power.