Skip to main content
European Commission logo print header

Hybrid Quantum Systems - Integrating Atomic/Molecular and Solid Sate Quantum Systems

Final Report Summary - HQS (Hybrid Quantum Systems - integrating atomic/molecular and solid state quantum systems)

The goal of the HQS project fellowship of Dr Majer was to combine different quantum technologies in order to realise hybrid quantum systems (HQS). In particular, the aim of the project was to combine ultracold atoms with superconducting devices. The role of Dr Majer was to introduce and establish the solid state physics and combine it with the technology of ultracold atoms which existed at the Technical University of Vienna.

At the beginning of the project we finalised our proposal and showed that an ensemble of ultracold atoms could be coupled to a superconducting transmission line resonator and that the system reached the strong coupling regime. Furthermore, we analysed strategies to increase the coupling strength and found, in collaboration with the group of G. Kurizki, that the coupling was enhanced by optically excited Rydberg states.

In parallel, Dr Majer made progress towards the experimental realisation of the proposal. He purchased and installed a dilution refrigerator system which allowed for the measurement of superconducting devices. Furthermore, he initiated the fabrication of superconducting resonators at the micro-fabrication facility of the Technical University of Vienna. The resonators were measured in the dilution refrigerator and showed quality factors up to a million, which was among the highest reached with this technology. In addition, the properties of the resonators with light impinging on the resonator were tested and provided significant information for the proposals relying on the manipulation with light pulses.

For the realisation of a cryogenic atom chip experiment, an electron beam driven alkali atom source was demonstrated. However, an alternative path was chosen, which implied a magnetic conveyor belt transport from a magneto-optical trap into a cryostat. For experimental simplicity, a 4 K fridge was installed. Since the resonator at 4 K was occupied with thermal photons, the coupling of atoms to a superconducting resonator at finite temperature was studied, in collaboration with the University of Innsbruck. Theoretically, we demonstrated that a strong coupling was possible even at finite temperatures.

Dr Majer also investigated alternative systems for the realisation of hybrid quantum systems. He initiated an experimental effort to measure nitrogen-vacancy colour centres in diamond. He coupled a diamond to a superconducting resonator and showed that with this hybrid quantum system an ensemble of nitrogen-vacancy spins could strongly couple to the superconducting resonator.