QUIET (experiment)

QUIET (experiment)
Name	QUIET
Country	United States
Field	Cosmology
Started	2008
Completed	2010
Collaborators	California Institute of Technology; University of Chicago; Princeton University; Johns Hopkins University; Stanford University

QUIET (experiment)

QUIET was a ground-based observational program to measure the polarization of the cosmic microwave background with focus on B-mode signals; it operated from a site in the Atacama Plateau and engaged researchers from institutions including the California Institute of Technology, University of Chicago, Princeton University, Johns Hopkins University and Stanford University. The project sought to probe theories linked to Inflation, test predictions from models related to the Big Bang, and constrain parameters tied to primordial gravitational waves and the tensor-to-scalar ratio via sensitive polarization measurements. QUIET's design, deployment, and analysis intersected with initiatives and collaborations such as BICEP, Planck (spacecraft), WMAP, and the South Pole Telescope community.

Introduction

QUIET was launched in the late 2000s as part of a cohort of CMB polarization experiments that also included arrays and teams at Harvard University, Massachusetts Institute of Technology, University of California, Berkeley, Caltech, and Columbia University. The collaboration built on technical heritage from experiments like DASI, CBI, POLARBEAR, and QUaD and engaged experts affiliated with observatories on the Atacama Plateau and programs funded or coordinated with agencies such as NASA, National Science Foundation, and international partners. The experiment targeted angular scales influenced by both recombination-era signatures and potential inflationary B-modes, relating to theoretical work by researchers connected to Alan Guth, Andrei Linde, and groups publishing in venues like Physical Review Letters and Astrophysical Journal.

Experimental Design and Instrumentation

QUIET employed coherent detector technology built around high-electron-mobility transistor amplifiers and modular polarimeter assemblies developed through collaborations with instrument teams at Jet Propulsion Laboratory, Lucent Technologies alumni groups, and engineering labs associated with Northrop Grumman subcontractors. The receiver arrays were integrated into Gregorian optics mounted on a telescope platform similar in concept to those used by teams from University of Chicago and Princeton University for other CMB efforts. Cryogenic systems and readout electronics incorporated designs influenced by work at Lawrence Berkeley National Laboratory and fabrication facilities affiliated with Stanford Linear Accelerator Center. The instrument was engineered to control polarization systematics by leveraging calibration references and hardware concepts that paralleled development at NIST, SRON Netherlands, and instrument groups linked to European Southern Observatory instrumentation programs.

Observations and Data Collection

Observations were conducted from a high, dry site on the Atacama Plateau to exploit low precipitable water vapor conditions; the site choice mirrored placements used by the Atacama Cosmology Telescope and POLARBEAR projects. Survey strategy prioritized deep integration on selected fields overlapped by ancillary data from WMAP and Planck (spacecraft) for cross-correlation and foreground separation, and that approach echoed field choices by teams at BICEP and Keck Array. The campaign collected polarized microwave sky maps across frequency bands chosen to mitigate contamination from Galactic synchrotron linked to sources catalogued by NVSS and from thermal dust emission studied by teams publishing in Monthly Notices of the Royal Astronomical Society. Scanning patterns, pointing models, and schedule logistics drew on operational experience similar to that at South Pole Telescope and facility procedures comparable to those at Chilean National Observatory collaborations.

Data Analysis and Results

The QUIET collaboration processed time-ordered data through pipelines implementing map-making, component separation, and power-spectrum estimation methods used by groups publishing in Physical Review D and by analysis teams from Planck Collaboration and WMAP. Results constrained the CMB E-mode polarization with signal-to-noise and placed upper limits on primordial B-mode amplitude and the tensor-to-scalar ratio r, contributing constraints complementary to those from BICEP2, Keck Array, and POLARBEAR. Statistical inference employed likelihood frameworks and Monte Carlo ensembles akin to methodologies from analyses associated with CosmoMC and public codes referenced by researchers at University of Cambridge and University of Oxford. QUIET's published results appeared in journals frequented by members of the American Astronomical Society and the European Astronomical Society.

Systematic Errors and Calibration

QUIET devoted significant effort to characterizing instrumental polarization, beam asymmetries, gain drifts, and correlated noise; calibration routines incorporated observations of astronomical calibrators such as planets used by teams at ALMA and compact sources catalogued by SMA, and internal calibration sources similar to hardware employed at NIST laboratories. Systematic-error budgets were developed in parallel with contemporaneous projects at Caltech and Harvard-Smithsonian Center for Astrophysics to isolate leakage between temperature and polarization and to correct for ground pickup analyzed with methods comparable to those described by Planck Collaboration papers. Cross-checks included jackknife tests and null maps following statistical prescriptions used by collaborations publishing in Journal of Cosmology and Astroparticle Physics.

Scientific Impact and Legacy

QUIET's constraints on polarized microwave anisotropy informed theoretical and observational programs pursued by teams at Princeton University, Harvard University, Stanford University, and international consortia including the European Space Agency community; its technical advances in coherent polarimeter arrays influenced subsequent instrument designs at institutions like NIST, NASA Goddard Space Flight Center, and university laboratories. The experiment's datasets and analysis practices provided cross-validation for results from Planck, BICEP/Keck, and POLARBEAR, contributing to the cumulative effort that shaped next-generation proposals such as CMB-S4 and informing theoretical work by scholars associated with Institute for Advanced Study, Perimeter Institute, and major research centers. QUIET's legacy persists in instrumentation concepts, calibration methodologies, and collaborative models adopted across the international CMB community.

Category:Cosmic microwave background experiments