Avalanche Photodiodes (APDs): These are semiconductor devices that operate in a high-gain mode to detect individual photons. They are widely used due to their high detection efficiency and fast response time. Photomultiplier Tubes (PMTs): These are vacuum tubes that amplify the signal produced by a single photon. PMTs are known for their high sensitivity and large dynamic range. Superconducting Nanowire Single-Photon Detectors (SNSPDs): These are ultra-sensitive detectors made of superconducting materials. They offer near-unity quantum efficiency and extremely low dark count rates, making them ideal for high-precision applications.
