g(2) is the second-order correlation function that quantifies the statistical correlation of photon emissions at two different times, providing insights into the nature of light sources. It is particularly important in distinguishing between classical and quantum light, helping to identify whether a light source is coherent or chaotic. This function plays a key role in understanding higher-order correlations in photon statistics.
congrats on reading the definition of g(2). now let's actually learn it.