Sensitivity of a Bolometric Interferometer to the CMB power spectrum

TL;DR

This paper compares the sensitivity of bolometric interferometry to direct imaging and heterodyne methods for detecting B-mode polarization in the CMB, highlighting its advantages and limitations.

Contribution

It introduces a sensitivity comparison framework for bolometric interferometry against other methods, emphasizing its potential as an alternative with lower systematic errors.

Findings

Bolometric interferometry is less sensitive than direct imaging.

It is more sensitive than heterodyne interferometry due to low bolometer noise.

Offers an alternative with potentially lower systematic errors.

Abstract

Context. The search for B-mode polarization fluctuations in the Cosmic Microwave Background is one of the main challenges of modern cosmology. The expected level of the B-mode signal is very low and therefore requires the development of highly sensitive instruments with low systematic errors. An appealing possibility is bolometric interferometry. Aims. We compare in this article the sensitivity on the CMB angular power spectrum achieved with direct imaging, heterodyne and bolometric interferometry. Methods. Using a simple power spectrum estimator, we calculate its variance leading to the counterpart for bolometric interferometry of the well known Knox formula for direct imaging. Results. We find that bolometric interferometry is less sensitive than direct imaging. However, as expected, it is finally more sensitive than heterodyne interferometry due to the low noise of the bolometers. It therefore appears as an alternative to direct imagers with different and possibly lower systematic errors, mainly due to the absence of an optical setup in front of the horns.