Development of microfabricated ion traps for scalable microwave quantum technology

Lekitsch, Bjoern (2015) Development of microfabricated ion traps for scalable microwave quantum technology. Doctoral thesis (PhD), University of Sussex.

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Abstract

Microfabricated ion traps are an important tool in the development of scalable quantum
systems. Tremendous advancements towards an ion quantum computer were made in
the past decade and most requirements for a quantum computer have been fulfilled in
individual experiments. Incorporating all essential capabilities in a fully scalable system
will require the further advancement of established quantum information technologies and
development of new trap fabrication techniques.

In my thesis I will discuss the theoretical background and experimental setup required
for the operation of ion traps. Measurement of the important ion trap heating rate was
performed in the setup and I will discuss the results in more detail.

I will give a review of microfabrication processes used for the fabrication of traps, outlining
advantages, disadvantages and issues inherent to the processes. Following the review I will
present my work on a concept for a scalable ion trap quantum system based on microwave
quantum gates and shuttling through X-junctions.

Many of the required building blocks, including ion trap structures with current-carrying
wires intended to create strong magnetic field gradients for microwave gates were investigated
further. A novel fabrication process was developed to combine current-carrying wires
with advanced multilayered ion trap structures. Several trap designs intended for proof of
principle experiments of high fidelity microwave gates, advanced detection techniques and
shuttling between electrically disconnected ion traps will be presented. Also the electrode
geometry of an optimized X-junction design with strongly suppressed rf barrier height will
be presented.

Further, I developed several modifications for the experimental setup to extend the existing
capabilities. A plasma source capable of performing in-situ cleans of the trap electrode
surfaces, which has been demonstrated to dramatically reduce the heating rate in ion
traps, was incorporated. I will also present a vacuum system modification designed to
cool ion traps with current-carrying wires and transport the generated heat out of the
vacuum system. In addition a novel low-noise, high-speed, multichannel voltage control
system was developed by me. The device can be used in future experiments to precisely
shuttle ions from one trapping zone to another and also to shuttle ions through ion trap
junctions.

Lastly I will outline the process optimization and microfabrication of my ion trap designs.
A novel fabrication process which makes use of the extremely high thermal conductivity of
diamond substrates and combines it with thick copper tracks embedded in the substrate
was developed. Large currents will be passed through the wires creating a strong and
controllable magnetic field gradient. Ion trap designs with isolated electrodes connected
via buried wires can be placed on top of the current-carrying wires, allowing the most
advanced electrode designs to be fabricated with current-carrying wires.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QC Physics > QC0170 Atomic physics. Constitution and properties of matter Including molecular physics, relativity, quantum theory, and solid state physics
Depositing User: Library Cataloguing
Date Deposited: 10 Jun 2015 10:55
Last Modified: 16 Oct 2017 12:08
URI: http://sro.sussex.ac.uk/id/eprint/54336

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