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 primordial gravitational waves which are theoretically expected to be produced during inflation at about 10-35 seconds after the Planck epoch. Their presence would be a non-trivial result concerning quantum gravity because tensor modes would mean the metric must be quantized. 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 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 their high sensitivity and interferometers with their exquisite control of instrument systematic effects. The interferometric nature of QUBIC also allows spectro-imaging giving improved spectral resolution concerning imagers, which is a significant advantage for foreground removal. The QUBIC Observatory was inaugurated in Nov. 2022 on its observing site at 5000m a.s.l. in the province of Salta in Argentina. The Technological Demonstrator is installed at the site and is currently undergoing commissioning. Observations are expected to start early in 2025.

In addition to participation in data acquisition and analysis 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 unique to QUBIC, that allows improved cleaning from the contamination of foreground emission.

• Implementing and using self-calibration to account 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-APC team at APC, with the rest of the collaboration in France, Italy, Ireland, and Argentina. 

Responsable(s) / Advisor(s): Jean-Christophe Hamilton (hamiltonapc.in2p3.fr), Steve Torchinsky (satorchiapc.in2p3.fr)

Niveau demandé / Requirements: M2 ou équivalent / Master, M.Sc.

Profil: Physique Fondamentale, Astrophysique, Instrumentation / Fundamental Physics, Astrophysics, Instrumentation