QUaD was a astronomical survey of CMB polarization, as well as the purpose-built telescope and polarimeter to carry it out. The polarimeter was a bolometer array with features to make it polarization-sensitive. The survey was carried out from a location adjacent to South Pole Station. The telescope had an aperture of 2.6 m. QUaD stood for QUEST at DASI, QUEST being an early name for the polarimeter, which for QUaD is mounted in the mounting previously used for DASI. The survey's aim was to detect both E-modes and B-modes.