December 2019

Abstracts of the QSIT Lunch Seminar, Thursday, December 5, 2019

Aharonov-Bohm cages with photonic waveguide arrays - The square-root of a topological insulator

Ioannis Petrides – Quantum Engineered Systems (Zilberberg group), ETH Zurich

Topological Insulators are a novel state of matter, where spectral bands are characterized by quantized topological invariants. In this talk, I will present the experimental implementation and topological characterization of a 1D insulator based on photonic Aharonov-Bohm cages.
Such insulator exhibits spectral bands with nonquantized indices, yet robust boundary states. A topological origin of the robustness will be provided, based on the quantization of the indices in the corresponding system where the square of the Hamiltonian is taken.

2-qubit quantum logic on an optics integrated ion trap

Chi Zhang - Trapped Ion Quantum Information Group (Home group), ETH Zurich

Trapped ions are one of the leading platforms for quantum information processing. To realize a practically useful quantum computer, one remaining challenge is to scale up the number of ions without losing the fidelity in their individual control. Integration of optics to the ion traps seems essential to meeting this challenge. It also removes some sources of gate infidelity thanks to the improved phase and beam pointing stability in the laser beam delivery, as well as allowing better use of laser power through tighter beam focusing. We are working on a surface-electrode ion-trap with integrated silicon nitride waveguides and grating couplers in a 4-Kelvin cryostat. We have used laser beams delivered by the integrated photonics to demonstrate the first multi-qubit gates using this approach, achieving a Bell state fidelity of 99.3% with two 40Ca+ ions. Characterization of the errors suggest possible further improvements. I will also give an outlook on the different types of integrated photonic chips which we have made, which are suited for various approaches to scaling.  

 

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