  A prototype version of the Q & U Bolometric Interferometer for Cosmology
(QUBIC) underwent a campaign of testing in the laboratory at Astroparticle
Physics and Cosmology in Paris. The detection chain is currently made of 256
NbSi Transition Edge Sensors cooled to 320 mK.The readout system is a 128:1
Time Domain Multiplexing scheme based on 128 SQUIDs cooled at 1K that are
controlled and amplified by an SiGe Application Specific Integrated Circuit at
40 K. We report the performance of this readout chain and the characterization
of the TESs. The readout system has been functionally tested and characterized
in the lab and in QUBIC. The Low Noise Amplifier demonstrated a white noise
level of 0.3 nV/sqrt(Hz). Characterizations of the QUBIC detectors and readout
electronics includes the measurement of I-V curves, time constant and the Noise
Equivalent Power. The QUBIC TES bolometer array has approximately 80% detectors
within operational parameters. While still limited by microphonics from the
pulse tubes and noise aliasing from readout system, the Noise Equivalent Power
is about 2E-16 W/sqrt(Hz), enough for the demonstration of bolometric
interferometry.
