Optical characterization of the quantum capacitance detector at 200 μm

We present the optical characterization at 200 μm wavelength of an antenna coupled quantum capacitance detector (QCD), a cryogenic detector based on a single Cooper pair box (SCB). The response of the device to a cryogenic blackbody source and the device noise have been measured giving an optical noise-equivalent power (NEP) at a readout frequency of 10 kHz of 2 × 10−17 W/Hz1/2 at an optical loading of 17 fW. For optical loadings of a few pW, the optical NEP was on the order of 10−16 W/Hz1/2, demonstrating that QCDs could already work as detectors for far-infrared and submillimeter wave radiation in a ground based telescope.