Eine planare mikrostrukturierte Paul-Falle mit integrierter Struktur für einen veränderbaren Magnetfeldgradienten

Laser-cooled atomic ions, stored in a Paul trap, can be used as
elementary quantum mechanical units for quantum information science.
For this purpose, addressing of individual ions and deterministic
coupling between the ions have to be provided. A static magnetic
field gradient applied to a Wigner crystal of trapped ions allows
for addressing of individual ions in frequency space, if the ions’
energy levels are magnetic field dependent. At the same time this
field gradient induces spin-spin coupling (magnetic gradient induced
coupling - MAGIC) between ions that can be used for conditional
quantum gates. Both, addressing and conditional quantum gates can be
carried out using radiation in the radio-frequency and microwave
regime.

In this thesis first results to use a surface trap in quantum
information science using MAGIC are presented. This novel kind of
ion trap is a miniaturized, segmented Paul trap with electrodes
placed in one single plane. Using micro-system technology for
fabrication it is possible to produce complex two-dimensional
electrode structures. During the course of this thesis the
infrastructure was established to produce a surface trap chip at our
institute. A trap chip was fabricated using optical lithography and
electroplating with a resulting electrode-thickness of 8,5 µm
and a surface roughness of 20-30 nm. This chip
integrates a novel current-carrying structure to provide an
arbitrary magnetic field distribution at the ions’ position.
Trapping of 172Yb+ ions with storage times of hours is
demonstrated. Employing radio frequency-optical double-resonance
spectroscopy the magnetic field gradient is characterized. For the
first time, individual addressing in frequency space in a surface
trap is demonstrated. For three ions an addressing fidelity of
F = 0,52(1) was demonstrated. This value is currently limited by
imperfections of the circuit paths of the carrier. In the near
future gradients up to 20 T/m should be achieved leading to an
addressing fidelity close to unity.