QUBIC I: Overview and science program

Abstract

The Q & U Bolometric Interferometer for Cosmology (QUBIC) is a novel kind of polarimeter optimized for the measurement of the B-mode polarization of the Cosmic Microwave Background (CMB), which is one of the major challenges of observational cosmology. The signal is expected to be of the order of a few tens of nK, prone to instrumental systematic effects and polluted by various astrophysical foregrounds which can only be controlled through multichroic observations. QUBIC is designed to address these observational issues with a novel approach that combines the advantages of interferometry in terms of control of instrumental systematic effects with those of bolometric detectors in terms of wide-band, background-limited sensitivity. The QUBIC synthesized beam has a frequency-dependent shape that results in the ability to produce maps of the CMB polarization in multiple sub-bands within the two physical bands of the instrument (150 and 220 GHz). These features make QUBIC complementary to other instruments and makes it particularly well suited to characterize and remove Galactic foreground contamination. In this article, first of a series of eight, we give an overview of the QUBIC instrument design, the main results of the calibration campaign, and present the scientific program of QUBIC including not only the measurement of primordial B-modes, but also the measurement of Galactic foregrounds. We give forecasts for typical observations and measurements: with three years of integration on the sky and assuming perfect foreground removal as well as stable atmospheric conditions from our site in Argentina, our simulations show that we can achieve a statistical sensitivity to the effective tensor-to-scalar ratio (including primordial and foreground B-modes) σ(r)=0.015.

Improved Constraints on Cosmic Birefringence from the WMAP and Planck Cosmic Microwave Background Polarization Data

“…To this end, both on-going and future groundbased [58][59][60][61][62][63][64][65][66], balloon-borne [67,68], and spaceborne [69,70] experiments are expected to lead to a convincing discovery (or otherwise) of cosmic birefringence. If proven to be a cosmological signal, isotropic cosmic birefringence would have a profound impact on cosmology, particle physics, and quantum gravity [71][72][73][74][75][76][77][78][79][80][81].…”

QUBIC II: Spectral polarimetry with bolometric interferometry

“…We can see that the Galactic dust is efficiently reconstructed in the 5 sub-bands as the residuals are compatible with pure noise. Note that the noise is not white but has spatial correlations due to the deconvolution with the multi-peak synthesized beam (see section 3.1.1 in Hamilton et al [24]). We also note that the residuals are higher on the edges than in the center of the sky patch.…”

“…In section 5.1 it was shown that a polychromatic interferometer has anti-correlations in neighbouring bands for each Stokes parameter. Furthermore, the spatial structure of noise is studied in detail in Hamilton et al [24] using end-to-end simulations. This allows us to build a fast noise simulator that reproduces efficiently the noise behaviour in the reconstructed maps.…”

“…The synthesized beam contains multiple peaks whose angular separation is linearly dependent on the wavelength. This paper does not attempt to make realistic simulations and forecasts for the QUBIC project, this is addressed in the companion paper Hamilton et al [24]. The goal is to demonstrate spectral imaging technique on simple cases, with very basic foreground models, not accounting for any systematic effect.…”

“…Detailed information about QUBIC can be found in the companion papers: scientific overview and expected performance of QUBIC [24], characterization of the technological demonstrator (TD) [25], transition-edge sensors and readout characterization [26], cryogenic system performance [27], half-wave plate (HWP) rotator design and performance [28 1. QUBIC main parameters (from Hamilton et al [24]) horn-switches system of the TD [29], and optical design and performance [30].…”