Daniel Klawson

EECS Department, University of California, Berkeley

Technical Report No. UCB/

December 1, 2025

Quantum computing promises exponential speed-up for problems that are intractable for classical machines. Ion traps are a leading platform for realizing a useful quantum device, where arrays of electrically confined, laser-addressed charged particles form the fundamental quantum bits (‘qubits’) used in information processing. Current state-of-the-art machines operate with around 100 qubits, but it is estimated that leading algorithms will need thousands of qubits (or more) to hold a practical advantage. Their control methods rely on bulk benchtop optics which limits component density due to the size and stability constraints. Therefore, photonic integration has been identified to shrink control optics and boost scalability, paving the way for higher-qubit ion trap systems.

In this dissertation, I introduce a new photonic architecture built from conventional 2D waveguides and novel 3D printed micro-optics. This hybrid guided-wave, free-space system combines the compact, stable nature of photonics with the high optical quality of free-space optics, offering the best attributes of both approaches. Our device achieves effectively achromatic beam focusing from 405 nm to 880 nm (and beyond) via a planar waveguide lens and a 3D-printed biconic mirror. Moreover, we have measured < -35 dB crosstalk at a 5 µm pitch for the 532 nm and 729 nm barium and calcium gate wavelengths, owing to micron-scale beam waists, surpassing the state-of-the-art. We integrate our 2D-3D photonics monolithically with a surface electrode trap, fabricated in a high-yield 6-inch wafer scale process.

To fully test the device, we demonstrate a robust ultra-high vacuum fiber packaging scheme to achieve sub 1 x 10-10 Torr base pressure, enabling deployment of our ion trap photonic circuit in-vacuum. We report stable ion trapping of barium and calcium ion pairs, and successful Rabi oscillation measurement in calcium via integrated delivery of 729 nm, 854 nm, and 866 nm light through our hybrid 2D-3D PIC. This technology lays the groundwork for scalable, manufacturable quantum hardware with broadband on-chip optics, hopefully unlocking the next generation of high-qubit ion-trap processors.

Advisors: Ming C. Wu

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BibTeX citation:

@phdthesis{Klawson:32000,
    Author= {Klawson, Daniel},
    Editor= {Wu, Ming C. and Sipahigil, Alp},
    Title= {2D-3D Photonics for Scalable Quantum Computing},
    School= {EECS Department, University of California, Berkeley},
    Year= {2025},
    Month= {Dec},
    Number= {UCB/},
    Abstract= {Quantum computing promises exponential speed-up for problems that are intractable for classical machines. Ion traps are a leading platform for realizing a useful quantum device, where arrays of electrically confined, laser-addressed charged particles form the fundamental quantum bits (‘qubits’) used in information processing. Current state-of-the-art machines operate with around 100 qubits, but it is estimated that leading algorithms will need thousands of qubits (or more) to hold a practical advantage. Their control methods rely on bulk benchtop optics which limits component density due to the size and stability constraints. Therefore, photonic integration has been identified to shrink control optics and boost scalability, paving the way for higher-qubit ion trap systems.  

In this dissertation, I introduce a new photonic architecture built from conventional 2D waveguides and novel 3D printed micro-optics. This hybrid guided-wave, free-space system combines the compact, stable nature of photonics with the high optical quality of free-space optics, offering the best attributes of both approaches. Our device achieves effectively achromatic beam focusing from 405 nm to 880 nm (and beyond) via a planar waveguide lens and a 3D-printed biconic mirror. Moreover, we have measured < -35 dB crosstalk at a 5 µm pitch for the 532 nm and 729 nm barium and calcium gate wavelengths, owing to micron-scale beam waists, surpassing the state-of-the-art. We integrate our 2D-3D photonics monolithically with a surface electrode trap, fabricated in a high-yield 6-inch wafer scale process.

To fully test the device, we demonstrate a robust ultra-high vacuum fiber packaging scheme to achieve sub 1 x 10-10 Torr base pressure, enabling deployment of our ion trap photonic circuit in-vacuum. We report stable ion trapping of barium and calcium ion pairs, and successful Rabi oscillation measurement in calcium via integrated delivery of 729 nm, 854 nm, and 866 nm light through our hybrid 2D-3D PIC. This technology lays the groundwork for scalable, manufacturable quantum hardware with broadband on-chip optics, hopefully unlocking the next generation of high-qubit ion-trap processors.},
}

EndNote citation:

%0 Thesis
%A Klawson, Daniel 
%E Wu, Ming C. 
%E Sipahigil, Alp 
%T 2D-3D Photonics for Scalable Quantum Computing
%I EECS Department, University of California, Berkeley
%D 2025
%8 December 1
%@ UCB/
%F Klawson:32000