Quantum efficiency is a measure used in various fields such as physics, engineering, and chemistry to quantify the efficiency of a device or system in converting incoming photons or particles into useful output signals or measurable quantities. It is a key parameter in the evaluation of devices such as photodetectors, solar cells, and cameras. Essentially, quantum efficiency measures the percentage of incident photons that are successfully detected, converted, or utilized by a device. A high quantum efficiency indicates a device is better at converting incoming photons into output signals, while a low quantum efficiency implies that a device is less effective at utilizing incoming photons. Researchers often study and optimize quantum efficiency to enhance the performance of devices and systems in various applications.