Abstract:

Cosmic microwave background (CMB) polarization is the ultimate probe of primordial gravity waves in the early universe, via the B-mode (or parity odd) signal on degree angular scales. A detection of such a signal would provide strong evidence of the inflation scenario and evidence for connection between quantum physics and gravity. In this talk, I will describe two experimental efforts, the Atacama B-mode Search (ABS) and the Multimode Survey Experiment (MuSE), highlighting their unique features. ABS has been in operation at a high-altitude site in Chile since 2012. It deploys 480 transition edge sensors and uses a warm continuously-rotating half wave plate (HWP). Our recent publication demonstrated that the HWP rejects the atmospheric contamination at high accuracy, leading to both competitive sensitivity and excellent systematic control. MuSE is a novel pathfinder proposal using highly multimoded bolometers. (A multimoded bolometer is capable of measuring multiple electromagnetic degrees of freedom simultaneously.) I will discuss how the proposed architecture can attain competitive sensitivity and polarization systematics control, thus complementing the development of single-mode bolometers. Development and demonstration of such unique instruments are critically important in order to detect the subtle B-mode signal.