Coherent rotations of qubits within a mixed-species surface ion trap

by Martin van Mourik (University of Innsbruck)

Wednesday 29 Apr 2020, 11:00 → 13:00 Europe/Stockholm

Fysikum equipment

https://stockholmuniversity.zoom.us/j/65444576560

Trapped ion-based qubits provide a promising platform for quantum computation. These systems have demonstrated a universal set of quantum gate operations necessary for performing arbitrary quantum algorithms, and are now reaching new frontiers in solving scalability challenges. One can imagine an ionic quantum information processor as a network of tracks along which ionic qubits can travel. Locally one can implement quantum gate operations, but the number of qubits to be jointly manipulated is limited. One challenge is to efficiently get ions on a track to pass each other, without deterring the qubit information stored in each ion. In this presentation, I will discuss a method to achieve such passing while maintaining qubit coherence, which involves rotating a chain of ions, trapped in a surface Paul trap. The lack of symmetry of the electrodes of a planar trap with respect to the trapping region makes this swap operation technically challenging. Therefore, adequate understanding and control of the time-dependent potentials applied to the ions is essential. I will discuss our methods of calibrating and determining these potentials, and how we use machine learning to optimize our control sequences to implement swap operations. Weachieve rotations on time scales shorter than typical laser-driven gates, while maintaining over 99% of quantum coherence. The presented methods of potential sequence parametrization and machine learning-based optimization can be easily generalized to other ion transport operations, such as transport along a track, and splitting of an ion register.