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Quantum devices in topological matter: carbon nanotubes, graphene, and novel superfluids

Periodic Reporting for period 3 - QuDeT (Quantum devices in topological matter: carbon nanotubes, graphene, and novel superfluids)

Reporting period: 2019-01-01 to 2020-06-30

The project addresses quantum devices in hybrid systems formed using carbon nanotubes, graphene, and superfluid helium. The aim is to develop and utilise ultra sensitive nano electromechanical resonators to investigate fundamental physics questions, to understand properties of these non-trivial materials, and to discover and create new quantum systems.

The project provides novel approach for the development of future quantum technologies, as well as analogies with other phenomena and systems of interest. While the 21st century is expected to be the era of quantum technology, a thorough understanding and control of quantum mechanical properties of matter will pave the way for these emerging technologies. The potential of harnessing quantum phenomena will open vast and unexpected industrial and economic opportunities for decades to come. New applications and advances with broad technological and societal impact are expected in quantum sensors, simulators, communication, and computing.
Several different types of ultra sensitive sensors have been constructed in the project. Graphene and carbon nanotube mechanical resonators make sensitive sensors due to their small mass and nearly ideal structure. At low temperatures, high quality factors can be reached, which facilitates detection of tiny frequency shifts or small variation in the resonance amplitude. The frequency shifts can be employed for mass or force detection while amplitude changes indicate altered dissipation.

We have employed the developed ultra sensitive sensors for generating new information on quantum systems with specific topological order. Among them, as an example, are emergent composite fermions (CF) in graphene in a large magnetic field. Force sensing has been employed to obtain first evidence of the Josephson force, which is a result of the interplay between superconducting phase dynamics and mechanical motion. First experiments using superconducting nanotube sensors in topological superfluid 3He have been made.
Superconducting nanotube sensors integrated in microwave cavities. Operation of such detectors in topological superfluid 3He and with coverage of a few atomic layers of 3He. Detection of new coherent phenomena in systems combing two topological materials, namely graphene and superfluid 3He.