Low-Crosstalk Silicon Fabricated Optical Waveguides for Laser Delivery to Matter Qubits

Abstract:

Matter qubits often rely on light delivery to induce changes in qubit states, which requires precisely applied external fields. The presence of unintended light, such as scatter from the laser source or output crosstalk could lead to unexpected qubit excitations, which destroys coherence and lowers fidelity of the system. Although the quality of these quantum systems depends on precisely targeting qubits at the µm scale often used in quantum networking schemes, it remains a difficult optical engineering challenge. We detail our efforts to produce a foundry-produced, micro-fabricated silicon nitride (SiN) optical waveguide to lower the intrinsic crosstalk of directly addressing unequally spaced trapped ions, which serve as model qubits for this system. Previous efforts to mitigate unintended crosstalk using optical splitters systems have been limited to order -40 dB which we surpass. The design improvements here pave the way for large scale light delivery with low crosstalk by improving chip architecture commonly utilized by these waveguide devices. Approved for Public Release; Distribution Unlimited: AFRL-2023-6150 / 2023-1138