509 research outputs found
Ultraclean carbon nanotubes and superconducting coplanar resonators: Materials, nano-electromechanics, and few-electron systems
Scope of the thesis was the investigation of nano-electromechanical properties of carbon nanotubes, the preparation of a reliable fabrication process and measurement setup for coplanar waveguides, and work towards a combination of both systems.
Regarding the properties of carbon nanotubes, numerical transmission calculations were performed for various chiralities in a parallel magnetic field to obtain a more detailed understanding of the transport spectrum. In addition, the numerical transmission calculations are compared to the experimental data and an analytic model.
The coupling of electrons and vibrons of the longitudinal stretching mode was observed in a suspended carbon nanotube. Analysis led to a magnetic field dependent Franck-Condon coupling factor.
Regarding coplanar waveguides, first measurements of niobium superconducting quarter wavelength resonators were presented; internal quality factors up to 240000 were observed. The low temperature behavior of the resonance frequency and the internal quality factor were both well described by changes in the kinetic inductance fraction and the loss due to two-level systems present in the substrate material
Classically entangled optical beams for high-speed kinematic sensing
Tracking the kinematics of fast-moving objects is an important diagnostic
tool for science and engineering. Existing optical methods include high-speed
CCD/CMOS imaging, streak cameras, lidar, serial time-encoded imaging and
sequentially timed all-optical mapping. Here, we demonstrate an entirely new
approach to positional and directional sensing based on the concept of
classical entanglement in vector beams of light. The measurement principle
relies on the intrinsic correlations existing in such beams between transverse
spatial modes and polarization. The latter can be determined from intensity
measurements with only a few fast photodiodes, greatly outperforming the
bandwidth of current CCD/CMOS devices. In this way, our setup enables
two-dimensional real-time sensing with temporal resolution in the GHz range. We
expect the concept to open up new directions in photonics-based metrology and
sensing.Comment: v2 includes the real-time measurement from the published version.
Reference [29] added. Minor experimental details added on page
Quantum-limited measurements of optical signals from a geostationary satellite
The measurement of quantum signals that traveled through long distances is of
fundamental and technological interest. We present quantum-limited coherent
measurements of optical signals, sent from a satellite in geostationary Earth
orbit to an optical ground station. We bound the excess noise that the quantum
states could have acquired after having propagated 38600 km through Earth's
gravitational potential as well as its turbulent atmosphere. Our results
indicate that quantum communication is feasible in principle in such a
scenario, highlighting the possibility of a global quantum key distribution
network for secure communication.Comment: 8 pages (4 pages main article, 4 pages supplementary material), 9
figures (4 figures main article, 5 figures supplementary material), Kevin
G\"unthner and Imran Khan contributed equally to this wor
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