Superconducting nanowire single-photon detectors for advanced photon-counting applications
Abstract
The ability to detect infrared photons is increasingly important in many
elds of scienti c endeavour, including astronomy, the life sciences and
quantum information science. Improvements in detector performance
are urgently required. The Superconducting Nanowire Single-Photon
Detector (SNSPD/SSPD) is an emerging single-photon detector technology
o ering broadband sensitivity, negligible dark counts and picosecond
timing resolution. SNSPDs have the potential to outperform conventional
semiconductor-based photon-counting technologies, provided the
di culties of low temperature operation can be overcome. This thesis
describes how these important challenges have been addressed, enabling
the SNSPDs to be used in new applications. A multichannel SNSPD
system based on a closed-cycle refrigerator has been constructed and
tested. E cient optical coupling has been achieved via carefully aligned
optical bre. Fibre-coupled SNSPDs based on (i) NbN on MgO substrates
and (ii) NbTiN on oxidised Si substrates have been studied. The
latter give enhanced performance at telecom wavelengths, exploiting the
re
ection from the Si=SiO2 interface. Currently, the detector system
houses four NbTiN SNSPDs with average detection e ciency >20% at
1310 nm wavelength. We have employed SNSPDs in the characterisation
of quantum waveguide circuits, opening the pathway to operating this
promising platform for optical quantum computing for the first time at
telecom wavelengths.