Interaction‐Free Quantum Spectroscopy

Abstract

Interaction‐free measurement (IFM)‐based single‐photon interference is developed as a powerful platform for revealing object information in quantum metrology, where the presence of a sample is identified without photon “touching” in an interferometer. Herein, a method of obtaining the spectroscopic properties with interaction‐free quantum spectroscopy (IFQS) based on the spectrum‐correlated photon pairs by the spontaneous parametric down‐conversion (SPDC) is proposed and implemented. Infrared signal photons around 1557 nm from the SPDC pairs are sent to a Mach–Zehnder interferometer (MZI), which contains a semitransparent sample in one of the arms. The transmission spectrum of the sample is characterized by recording the coincidence detection of the spectrum‐correlated near‐infrared heralding photons around 808 nm from the SPDC. The IFQS can not only distinguish the existence of the sample but also recognize the sample by its transmission spectrum without interaction. The approach unlocks the potential to facilitate the applications of correlation‐based quantum spectroscopy and reduce the power‐induced optical damage of fragile materials.

Keywords

• correlation-based spectroscopy
• interaction-free measurement
• spontaneous parametric down-conversion