Superconducting nanowire single-photon detectors
(SNSPD or SSPD)
SNSPD are considered the fastest single-photon detectors (SPD) for photon counting and are considered as key technology for quantum optics and optical quantum technologies.
Superconducting nanowire single photon detectors are based on the principle of superconducting detection. A superconducting material conducts electric current without any resistance when cooled below a critical temperature called the transition temperature. When a photon hits such a detector, it is absorbed, causing a pair of electrons called a Cooper pair to form. The formation of the Cooper pair causes a decrease in the electrical resistance of the superconducting material, which is registered as a signal.
Superconducting nanowire single photon detectors offer high sensitivity and high temporal resolution with very high count rates, very short dead times, and very low temporal jitter compared to other single-photon detectors. They can detect single photons at very low intensity, making them ideal for quantum communications, quantum cryptography and quantum computing. Because they are based on superconducting technology, they also have a very low background rate, which means they are very accurate and do not cause false alarms.
However, using superconducting nanowire single photon detectors also has disadvantages. One of the biggest drawbacks is that they usually need to be cooled to very low temperatures, usually below 4 Kelvin (-269°C). This requires special cooling equipment, which can be expensive and impractical. In addition, they have a limited detection area and are therefore not suitable for covering large areas.
Overall, superconducting nanowire single photon detectors offer high sensitivity and high temporal resolution, but may not be suitable for all applications due to their technical limitations.