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Interaction between microwave radiation and magnetic qubits

A strong work on the interaction between microwave radiation and molecular magnets was performed by the UB group. Efforts focused on two main problems:

- First, the analysis of the electromagnetic radiation accompanying the fast demagnetisation process in molecular magnets and,
- Second, performing new experiments to better understand the spin tunnelling transitions in the case of extremely high sweep of the bias magnetic field.

In fact, these two works connected the behaviour of our magnetic units as qubits and the superradiance emission.

The experiments to better analyse the electromagnetic radiation coming from molecular magnets were performed using:
a) different molecular magnets to correlate the chemical and nuclear properties of the magnetic unit with the probability of emission of radiation,
b) under different experimental conditions to study the influence of the temperature, magnetic field and number of molecules on the power emission of the electromagnetic radiation,
c) using different waveguides to better correlate the power transmission with the geometry, diameter, length and material, of the waveguides, and
d) using very fast detection methods for the magnetization change and radiation detection.

The main aim of the experiments performed at ultra high sweep of the bias magnetic field was to test the Landau Zener transition probability in the spin tunnelling case. It is well established that single quantum transitions obey the Landau Zener law. In our experiments, however, we have seen that this law is not obeyed anymore and this has been interpreted as due to the simultaneous transition of a huge number of spin levels. This result provides strong evidence for the occurrence of the superradiance emission. These experiments are also crucial to better understand the qubit behaviour of the magnetic clusters when working as logic gates.

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