QUBIC, a bolometric interferometer to measure the B-modes of the CMB

International audience; 3rd ARENA Conference: An Astronomical Observatory at CONCORDIA (Dome C, Antarctica)L. Spinoglio and N. Epchtein (eds)EAS Publications Series, 40 (2010) 399-404QUBIC, a bolometric interferometer to measure the B-modes of the CMBJ.-C. Hamilton and R. CharlassierLaboratoire APC, Université Paris Diderot, Paris 7, CNRS, IN2P3, 10 rue Alice Domon et Léonie Duquet, 75205 Paris, France The quest for the B-modes in the CMB polarization is one of the main challenges of modern cosmology as it would allow to give sharp constraints on the inflationary period.One of the main challenges of B modes detection is the treatment of systematic errors. Comparison of observations subject to different systematics is crucial. Interferometers offer such an alternative to imagers. However, to obtain the required sensitivity, a very large number of baselines is needed, which is extremely difficult to achieve with heterodyne interferometry. Bolometric interferometry copes with this problem using a new technique: the interference pattern produced by a few hundred horns is imaged on a bolometer array, and a time modulation of phase shifts insures the separation of visibilities while coherently adding redundant ones. The QUBIC collaboration proposes to build such an instrument.