The quest for B-mode polarization of the Cosmic Microwave Background is among the main challenges in Observational Cosmology. Measurement of B-mode polarization in the CMB will be clear evidence of the presence of primordial gravitational waves which are theoretically expected to be produced during inflation about 10-35 seconds after the Planck epoch. The B-mode measurement is perhaps the most difficult cosmological challenge because the expected signal is very small.  It requires high sensitivity and negligible instrument systematic effects with wide frequency coverage in order to separate the primordial signal from foreground emissions.

QUBIC (QU Bolometric Interferometer for Cosmology: http://qubic.org.ar) is a novel instrument concept dedicated to the search for B-modes by measuring the Q and U polarization modes.  It brings together the advantages of bolometers with high sensitivity and those of interferometers that have exquisite control of instrument systematic effects. The interferometric nature of QUBIC also allows spectro-imaging and improved spectral resolution with respect to imagers, providing a significant advantage concerning foreground removal. The Technological Demonstrator was inaugurated in Nov. 2022 at the QUBIC site at 5000m a.s.l. in the province of Salta in Argentina and is currently undergoing commissioning. Observations are expected to start early in 2024.

Besides participating in data taking and exploitation of QUBIC (including travel to Argentina), the Ph.D. student will participate in the following topics:

• Developing the data analysis pipeline: time-domain raw data processing, filtering, map reconstruction, angular power spectrum measurement, and cosmological constraints, especially using the spectral-imaging technique, specific to QUBIC, that allows improved cleaning from the contamination of foreground emissions.

• Implementing and exploiting self-calibration and accounting for instrumental systematic effects in the data analysis pipeline

• developing data analysis techniques based on Artificial Intelligence for the QUBIC data analysis pipeline: raw data cleaning, map-making, component separation, and cosmological parameters estimation.

The student will work within the QUBIC team at APC, collaborating with the rest of the collaboration in France, Italy, Ireland, and Argentina.