Cryogenic ion trapping for next generation quantum technologies

De Motte, Darren C.E. (2016) Cryogenic ion trapping for next generation quantum technologies. Doctoral thesis (PhD), University of Sussex.

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Abstract

Quantum technology has made great strides in the last two decades with trapped ions
demonstrating all the necessary building blocks for a quantum computer. While these
proof of principle experiments have been demonstrated, it still remains a challenging task
to scale these experiments down to smaller systems. In this thesis I describe the development
of technology towards scalable cryogenic ion trapping and quantum hybrid systems.
I first discuss the fundamentals of ion trapping along with the demonstration of ion
trapping on a novel surface electrode ion trap with a ring shaped architecture. I then
present the development of a cryogenic vacuum system for ion trapping at ~4 K, which
utilizes a closed cycle Gifford McMahon cryocooler with a helium gas buffered ultra-low
vibration interface to mechanically decouple a ultra-high vacuum system. Ancillary
technologies are also presented, including a novel in-vacuum superconducting rf resonator,
low power dissipation ceramic based atomic source oven and an adaptable in-vacuum
permanent magnet system for long-wavelength based quantum logic.
The design and fabrication of microfabricated surface ion traps toward quantum hybrid
technologies are then presented. A superconducting ion trap with an integrated high
quality factor microwave cavity and vertical ion shuttling capabilities is described. The
experimental demonstration of the cavity is also presented with quality factors of Q6~6000
and Q~15000 for superconducting niobium nitride and gold based cavities respectively,
which are the highest demonstrated for microwave cavities integrated within ion trapping
electrode architectures. An ion trap with a multipole electrode geometry is then presented,
which is capable of trapping a large number of ions simultaneously. The homogeneity of
five individual linear trapping regions are optimized and the design for the principle axis
rotation of each linear region is presented. An overview of microfabrication techniques used
for fabricating surface electrode ion traps is then presented. This includes the detailed
microfabrication procedure for ion traps designed within this thesis.
A scheme for the integration of ion trapping and superconducting qubit systems as a
step towards the realization of a quantum hybrid system is then presented. This scheme
addresses two key diffculties in realizing such a system; a combined microfabricated ion
trap and superconducting qubit architecture, and the experimental infrastructure to facilitate
both technologies. Solutions that can be immediately implemented using current
technology are presented. Finally, as a step towards scalability and hybrid quantum systems,
the interaction between a single ion and a microwaves field produced from an on
chip microwave cavity is explored. The interaction is described for the high-Q microwave
cavity designed in this thesis and a 171Yb+ion. A description of the observable transmission
from the cavity is described and it is shown that the presence of a single ion can
indeed be observed in the emission spectrum of high-Q microwave cavity even in the weak
coupling regime.

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: 03 Jan 2017 13:03
Last Modified: 03 Jan 2017 13:03
URI: http://sro.sussex.ac.uk/id/eprint/66011

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