The ever-increasing data sharing demands of modern technologies forces scientists to adopt new methods that can surpass the approaching limits of classical physics. Quantum optical communications and information, based on single-photon detectors offer the most promising possibility to reach new levels of data rate and communication security. Superconducting nanowire single-photon detectors (SNSPDs) have already been used in the past to demonstrate new protocols of quantum key distribution and are currently the best single-photon detection technology to enable quantum optical communication. With the goal creating a global quantum communication network, both optical fiber and free-space optical communication technologies have been explored. In addition, the scientific community started pursuing smaller and cheaper cryogenic solutions to enable the use of SNSPDs on a large scale. In this thesis, I describe the design and development of a cryogenic SNSPD receivers in free-space and optical-fiber configurations for 1550-nm-wavelength. The first configuration was created with the goal of enabling optical communication in the mid-IR. I present future steps to achieve this goal. The second configuration was designed to enable a compact and scalable integration of multiple SNSPD channels in the same system. Our approach has the potential of enabling SNSPD systems with more than 64 channel.
Thesis Supervisor: Professor Karl Berggren