Entanglement-Assisted Absorption Spectroscopy by Hong-Ou-Mandel Interference

Absorption spectroscopy has long been hailed as an absolute necessity for detecting the properties of complex chemical and biological samples. While conventional spectroscopy using classical light is severely limited by shot noise and lacks robustness against experimental imperfections, quantum light offers an avenue to perform absorption spectroscopy with provable advantages in the technical operations and the measurement precision. Here, we present an experimental approach to implement entanglement based absorption spectroscopy with the assistance of Hong-Ou-Mandel interference. Since the temporal interference fringe is determined by the spectrum pattern, a maximum-likelihood decision is sufficient for revealing the relevant quantum information about the absorptive properties of the test samples. These experimental results may significantly facilitate the use of quantum interferometric spectroscopy to practical applications, which may be particularly relevant for photon-sensitive biological and chemical samples.