Quantum Fast Spin dynamics addressed by High-Tc superconducting circuits

Nanoscopic spin excitations in confined geometries open a wide range of opportunities both for fundamental investigations and for applications.

However, quantum magnetization dynamics in nanomagnets are still largely unexplored, especially when it comes to non-homogeneous spin configurations.

QFaST is aimed at filling this gap by investigating quantum properties of magnetic vortices stabilized in low-damping ferromagnetic microdiscs at millikelvin temperatures.

The project will be built upon quantum nanocircuits based on the high critical temperature superconductor YBa2Cu3O7 (YBCO) in the form of nano Superconducting Quantum Interference Devices (nanoSQUIDs) and coplanar waveguide resonators.

On the one hand, quantum spin dynamics from quaistatic up to nanosecond timescales will be addressed with few Bohr magnetons-sensitivity and 100 nm spatial-resolution by implementing a broadband on-chip YBCO-nanoSQUID microscope.

This will be combined with the possibility of locally probing and controlling the temperature of the sample and sending radiofrequency pulses. Among other issues, such facility will allow studying zero-point vacuum fluctuations of vortex gyration. On the other hand, the physics of vortex gyration will be addressed by quantum cavity electrodynamics.

The first step towards this goal will be the experimental realization of vortex-photon hybrid states using YBCO resonators. Such achievement entails the exchange of vortex and photon populations in the form of Rabi oscillations.

Based on this, strong coupling of high order vortex modes and cavity photons will be explored putting emphasis in the possibility of transducing single photons into coherent spin-waves.

These studies will open new opportunities for future research, e.g., to transduce between microwave and optical photons or to manipulate and detect single quanta of vortex gyration, which are relevant for quantum information applications and detection of dark matter.