Superconducting qubits as sensors to detect dark matter in tunable cavities.

A leading candidate to explain the existence of dark matter in the Universe is the axion, which is detectable in experiments that use resonant cavities embedded in a strong magnetic field to turn an ambient axion of the dark matter halo of the Milky Way into a resonant photon. Superconducting qubits can be used to detect these photons without absorbing them, allowing for multiple detections of the same photon with minimal noise at mK temperatures, as demonstrated by Dixit et al. 2019. One of the collaborations working to make this detection possible is RADES, as part of the International IAXO Collaboration, of which the University of Barcelona is a member. 

Two master thesis are proposed to develop this project in the context of the RADES Collaboration. Im the first, the goal is to acquire experience working with qubits to reliably perform these single-photon detections, to reproduce the results of measurements of the quantum state of the qubit that indicates the presence or absence of a resonance photon, measure the qubit coherence time in different physical conditions, and optimize the detection and analysis method. For this, the master student will travel to work with RADES collaborators in Paris or Aalto (Finland) where the cryogenic laboratories and qubits to be used will be available. 

The second master thesis project focuses on tuning of the cavity resonant frequency by means of a ferromagnetic crystal inserted into the cavity that modifies the frequency through a variation of the magnetic permeability of the crystal with the magnetic field strength. This experimental project is to be performed in collaboration with the ICMAB, where a 16T magnet will be used to test a cavity and crystal developed in RADES.