An injection-locked 1762 nm laser for trapped barium ion qubits

Andrei Fedotov, Iuliia Zalesskaia, Petteri Uusimaa

J.S. Salacka

Kristina P. Galstyan, Ilia V. Zalivako, D. S. Kryuchkov +1 more

Anatoliy A. Savchenkov, Justin E. Christensen, David Hucul +4 more

Compact, high power lasers with narrow linewidth are important tools for the manipulation of quantum systems. We demonstrate a compact, self-injection locked, Fabry-Perot semiconductor laser diode with high output power at 493 nm. A high quality factor magnesium fluoride whispering gallery mode resonator enables both high passive stability and 1 kHz instantaneous linewidth. We use this laser for laser-cooling, in-situ isotope purifcation, and probing barium atomic ions confined in a radio-frequency ion trap. The results here demonstrate the suitability of these lasers in trapped ion quantum information processing and for probing weak coherent optical transitions.

Isaline Duperon

For optical qubit encoding, laser phase noise limits the coherence time for qubit manipulations.In this thesis, we address this challenge by replicating a low-phase-noise laser system for qubit manipulation of trapped ions in a cryogenic environment. Using injection locking technology, we inject a laser diode with another laser, ensuring the replicated light retains the same spectral properties. We describe the implementation of this technique, analyse its impact on the laser spectrum, and validate it by comparing its coherence time on a trapped-ion qubit with the previously used laser.Our results demonstrate that the new laser system preserves the coherence time achieved with the seed laser, with a qubit coherence time of $T_{coh}= \SI{2.52\pm0.15}{\milli\second} $, paving the way for scalable and robust quantum computing and simulation in the cryogenic setup. In the future, the laser phase noise may be further reduced by spectral filtering techniques with a narrowband optical cavity. This work contributes to overtake one of the key obstacles in trapped-ion quantum computation: having long qubit coherence time.

Weiran Ye, Jin‐Ming Cui, Yan Chen +5 more