June 2017

Abstracts of the QSIT Lunch Seminar, Thursday, June 8, 2017

Ultra-sensitive diamond nanoladder cantilevers

Martin Héritier – Spin Physics and Imaging (Degen group), ETH Zurich

Enhancing the mass and force detection sensitivity of mechanical resonators is of considerable interest for many applications. We present here a novel diamond `nanoladder' cantilever design that minimizes mechanical dissipation and achieves an ultrahigh force sensitivity of 196 ± 30 zN Hz^-1/2 at 160 mK, better than any other cantilever device to date. In combination with the best available magnetic field gradient of 28 x 10⁶ T m^-1, this sensitivity corresponds to detecting the magnetic moment of a single proton within one second. Such exceptional force sensitivity is possible due to a low mass, low spring constant, and high quality factor. Our design is inspired by carbon nanotubes which achieve maximum stability with a minimal mass. In contrast to carbon nanotubes, our nanoladder cantilevers can be batch fabricated with standard procedures and may be implemented in a great range of different force sensing applications. In particular, we plan to use these resonators for magnetic resonance force microscopy.

Studying the Functional Quantum Biology of Light-Harvesting Processes with Superconducting Circuits

Anton Potočnik – Quantum Device Lab (Wallraff group), ETH Zurich

The process of photosynthesis is despite almost a century long investigation still not fully understood. With recent observations of quantum coherent effects in light harvesting protein complexes the interesting question whether an interplay of quantum and classical effects can play an important functional role in biological processes emerged. In particular, the high efficiency of the energy transport has been theoretically shown to result from such an interplay. Testing these ideas in biological systems is extremely challenging due to an immense molecular complexity and the lack of precise control of system parameters. Comprehensive model systems are therefore needed to verify the models and gain an experimental insight into the basic concepts behind energy transfer in disordered systems. To address this problem we employ an analog quantum simulator based on superconducting circuits to study energy transport in a system of three qubits exposed to Markovian and non-Markovian environments. Our results show the existence of an optimal noise power that maximizes the energy transport, which is in good agreement with the theoretical models of noise-assisted transport. Furthermore we show that highly structured non-Markovian environments can lead to higher transfer efficiencies where transport is highly sensitive to the features of the noise spectrum. These observations are also relevant for understanding olfactory processes giving rise to the sense of smell.

Coauthors:
A. Bargerbos,¹ F. A. Y. N. Schröder,² S. A. Khan,³ M. C. Collodo,¹ S. Gasparinetti,¹ Y. Salathé,¹ C. Creatore,² C. Eichler,¹ H. E. Türeci,³ A. W. Chin,² A.Wallraff^1
1Department of Physics, ETH Zürich, CH-8093 Zurich, Switzerland.
² Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
³ Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA.