QUBIC is a cosmology project to study

cosmic inflation In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the very early universe. Following the inflationary period, the universe continued to expand, but at a slower ...

by measuring the B-modes of the polarization of the

Cosmic Microwave Background The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dar ...

(CMB), by observing the sky with a

millimeter wave Extremely high frequency (EHF) is the International Telecommunication Union designation for the band of radio frequencies in the electromagnetic spectrum from 30 to 300 gigahertz (GHz). It is in the microwave part of the radio spectrum, between t ...

radio telescope A radio telescope is a specialized antenna (radio), antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the r ...

interferometer Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

. It uses bolometric

interferometry Interferometry is a technique which uses the ''interference (wave propagation), interference'' of Superposition principle, superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important inves ...

, which combines the advantages of interferometry (reduction of systematic errors) and those of the bolometer detectors (high signal sensitivity). QUBIC observes the sky at two frequencies, 150 and 220 GHz, so that it can separate the cosmological signal from foreground emission, in particular thermal

dust Dust is made of particle size, fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian processes, aeolian process), Types of volcan ...

emission. The QUBIC project began in 2008 with the merger of BRAIN and MBI projects. A technical demonstrator of the instrument is being manufactured and should be tested in France in 2017. On 26 October 2022 the first module was installed and began operating. QUBIC is an international collaboration involving universities and laboratories in Ireland, France, Italy, Argentina, the U.K. and the U.S.A.

Observing instrument

The observing instrument is a

contained in a

cryostat A cryostat (from ''cryo'' meaning cold and ''stat'' meaning stable) is a device used to maintain low cryogenic temperatures of samples or devices mounted within the cryostat. Low temperatures may be maintained within a cryostat by using various ...

which is cooled to 4K with pulse tube coolers, to avoid contaminating the received signal with thermal radiation. The millimeter waves pass through a 45 cm polyethylene window in the cryostat and then through a rotating

half-wave plate A waveplate or retarder is an optical device that alters the polarization state of a light wave travelling through it. Two common types of waveplates are the ''half-wave plate'', which rotates the polarization direction of linearly polarized ligh ...

which modulates the polarization, followed by a polarizing grid which selects one of the two polarizing angles. The radiation then passes through an array of 400 microwave horns which

Observing site

Since millimeter waves are absorbed by water vapor in the atmosphere the device must be located at high altitudes above most of the atmosphere. The instrument has been installed at the

Large Latin American Millimeter Array The Large Latin American Millimeter Array (LLAMA) is a single-dish 12 m Nasmyth optics antenna which is under construction in the Puna de Atacama desert in the Province of Salta, Argentina, next to the Qubic experiment. The primary mirror ...

(LLAMA) site at Alto de Chorillo near

Salta, Argentina Salta () is the capital and largest city in the Argentine province of the same name. With a population of 618,375 according to the 2010 census, it is also the 7th most-populous city in Argentina. The city serves as the cultural and economic c ...

, at an altitude of .

References

{{CMB experiments Astronomical instruments Cosmic microwave background experiments