Phase Shift Sequences for an Adding Interferometer

TL;DR

This paper introduces a systematic method for designing phase shift sequences in bolometric interferometers, optimizing orthogonality and efficiency to enhance sensitivity in CMB polarization measurements.

Contribution

It presents a novel approach for constructing phase shift sequences that improve noise minimization and signal readout efficiency in bolometric interferometry.

Findings

Sequences achieve near-orthogonality, reducing noise.

Simultaneous readout of equivalent baselines improves SNR.

Method balances sequence length and phase shift complexity.

Abstract

Cosmic microwave background (CMB) polarimetry has the potential to provide revolutionary advances in cosmology. Future experiments to detect the very weak B mode signal in CMB polarization maps will require unprecedented sensitivity and control of systematic errors. Bolometric interferometry may provide a way to achieve these goals. In a bolometric interferometer (or other adding interferometer), phase shift sequences are applied to the inputs in order to recover the visibilities. Noise is minimized when the phase shift sequences corresponding to all visibilities are orthogonal. We present a systematic method for finding sequences that produce this orthogonality, approximately minimizing both the length of the time sequence and the number of discrete phase shift values required. When some baselines are geometrically equivalent, we can choose sequences that read out those baselines simultaneously, which has been shown to improve signal to noise ratio.