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Machine Learning-Enhanced Integrated Optical Couplers for Trapped Ion Qubits

Melika Momenzadeh, Maxim R. Shcherbakov

Published Jan 1, 2025• 0 citations
Publisher

Abstract

We propose machine learning-driven grating coupler in silicon nitride for trapped Ca+ ion qubit manipulation, achieving −28.3 dB crosstalk, 0.56 μm beam radius, and 34% efficiency, paving the way to high-fidelity trapped-ion quantum information systems..
DOI
10.1364/cleo_at.2025.jps200_106

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Trapped ions are one of the most advanced platforms for quantum technologies, with applications ranging from quantum computing to precision timekeeping. A crucial step towards more compact and scalable systems involves integrating photonic integrated circuits (PICs) into surface ion traps to enable on-chip light delivery and optical addressing of individual ions. Currently, most implementations rely solely on transverse-electric (TE) mode grating couplers, where the emitted light is polarized in the plane of the chip. In this work, we design, fabricate and characterize key silicon nitride (Si3N4) PIC components required for scaling trapped-ion based quantum systems to multiple operating zones, including incoupling structures, splitters, and grating couplers that support both TE and transverse-magnetic (TM) modes with comparable optical losses. We benchmark the PIC at 760 nm, which is a typical wavelength for Yb+-applications. The fabricated grating couplers enable the outcoupling of collimated free-space beams for both polarizations, exhibiting distinct emission angles. This dual-polarization capability gives more flexibility in polarization control and expands the accessible optical design space for trapped-ion quantum technologies.
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In this work, we report the design and optimization of photonics interposer for addressing trapped ion in a quantum computing system. The interposer is built on commercial SOI platform comprising of grating couplers and waveguide. 1,092 nm light beam can be coupled into the input coupler and propagates along the waveguide, which is eventually directed towards the trapped 88Sr+ ion qubit. Considering the coupling efficiency of both input and output coupler, the power efficiency reaching the trapped ion can be estimated to be ∼ 16%, and the output 1,092 nm light can be coupled onto the trapped ion qubit for addressing.
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