Quantum Seminar: Scalable technologies for surface-electrode ion traps
Dr. Zhang Chi, ETH Zurich
Trapped ions are a promising platform for practical quantum computing, with all the elementary building blocks realized with high quality. Currently, one outstanding challenge is to increase the number of trapped-ion qubits. In this talk, I will present several technologies that can facilitate the scaling up of trapped-ion quantum computers based on surface-electrode traps.
I will present a junction structure that interconnects modular ion trap units to form two-dimensional arrays. It is designed using a bi-objective optimization method, which maintains pseudo-potential confinement while minimizing the axial pseudo-potential gradient in the vicinity of the junction center. To facilitate the laser light delivery for parallel operation of the trapped-ion qubits in multiple trap sites, we implemented integrated optics in the trap, with which we realized high-quality quantum control of the ions, including a Mølmer–Sørensen gate with 99.3% Bell-state fidelity. We found that the light fields emitted by the integrated optics are more complicated than those typically produced in the far-field of free-space optical systems. I will present our observations and theoretical efforts in explaining the interaction between the ions and the integrated light field.
Extending the depth of quantum circuits is also necessary for large-scale quantum computation. I will present a hybrid operation scheme using Zeeman and optical qubits, which reduces the requirement for long-term optical phase stability and optical phase tracking in extended quantum logic sequences. I will also present a scheme and the results in preparing two Zeeman qubits into a maximally entangled state via collective optical pumping.
Reference: Nature 586, 533 (2020)