Measuring Brownian motion of MFM-tips & Characterizing mechanical properties of mono-crystalline diamond resonators

Measuring Brownian motion of MFM-tips & Characterizing mechanical properties of mono-crystalline diamond resonators

Baart, T.A.

Lukin, M.D. (mentor)
Kolkowitz, S.J. (mentor)
Unterreithmeier, Q.P. (mentor)

Applied Sciences

Quantum Optics Group, Harvard University

2011-08-29

In this project two main goals have been pursued: (1) measure the Brownian motion of a magnetic force microscopy-tip (MFM-tip) using either standard optical interferometry or through transmission modulation of a tapered fiber, and (2) measure the mechanical properties (quality factor and resonant frequency) of mono-crystalline diamond resonators. The results of the first experiment can be used to verify a similar experiment that currently tries to measure the Brownian motion of the same MFM-tip, but then in a more complicated setup that couples the motion of the resonator to the state of a nitrogen vacancy center (NV-center, i.e. an example of a spin qubit). The measurements shown in this report are in very good agreement with the theoretical expected value of Brownian motion and can be made using either optical interferometry of through tapered fibers. The NV-experiment has not yet been conclusive, so that comparison has not yet been made. The second goal is interesting as it will be the first time that someone tries to measure the mechanical properties of mono-crystalline diamond resonators. It is expected that the monocrystallinity will lead to high quality factors. Besides, the resonators themselves can now contain spin qubits (NV’s ‘live’ inside diamond) allowing one to perform new types of experiments to couple a qubit to a resonator. This report will show two frequency spectra of such resonators measured through optical interferometry in a vacuum chamber. The resonant frequencies agree with the expected value from Euler-Bernoulli beam-theory. The precise shape of the resonances is not yet fully understood. It is non-Lorentzian and seems to consist of two slightly separated peaks. It is therefore not yet possible to give a conclusion on the possible high quality factors of such resonators. Recommendations are given on how to improve the experiment and continue this line of research.

mechanical resonators
NV
monocrystalline diamond
tapered fiber
quality factor
Brownian motion
interferometry

http://resolver.tudelft.nl/uuid:7576893f-ff65-484e-b32c-3865f4d534ed

2011-11-19

Student theses

master thesis

(c) 2011 Baart, T.A.