  We demonstrate a high temperature performance quantum detector of Terahertz
(THz) radiation based on three-dimensional metamaterial. The metamaterial unit
cell consists of an inductor-capacitor (LC) resonator laterally coupled with
antenna elements. The absorbing region, consisting of semiconductor quantum
wells is contained in the strongly ultra-subwavelength capacitors of the LC
structure. The high radiation loss of the antenna allows strongly increased
collection efficiency for the incident THz radiation, while the small effective
volume of the LC resonator allows intense light-matter coupling with reduced
electrical area. As a result, our detectors operates at much higher
temperatures than conventional quantum well detectors demonstrated so far.
