High performance photon detector for qubit discrimination in 1550nm : Quantum information technology

A photon detector combining the two avalanche photodiodes (APD) has been demonstrated for qubit discrimination in 1550nm. Spikes accompanied with the signals in gated-mode were canceled by balanced output from the two APDs. The spike cancellation made it possible to reduce the threshold in the discriminators, and thus the gate pulse voltage. The dark count probability and afterpulse probability were reduced to 7×10 -7 and 10 -4 , respectively, without affecting the detection efficiency (11%) at 178K.