  Numerous molecules exhibit unique absorption bands in the fingerprint
infrared (IR) region, allowing chemical identification and detection. This
makes IR spectroscopy an essential tool in biomedical diagnostics, sensing, and
material characterization. However, measurements in the IR range are
challenging due to the relatively poor performance, need for cryogenic cooling,
and high cost of IR light sources and photodetectors. Here, we demonstrate that
the mid-IR fingerprints of the sample can be revealed from measurements in the
near-IR range using conventional silicon photodetectors. Our approach relies on
the quantum interference of correlated photon pairs produced in strongly
frequency non-degenerate parametric down-conversion. Our technique
simultaneously measures the absorption coefficient and refractive index in the
broad fingerprint region with high accuracy. As a proof-of-concept, we perform
spectroscopy of nitrous oxide gas in the 7.4-8.4 {\mu}m wavelength range, with
the detection in the 865-877 nm range. This work extends the applicability of
quantum interferometry to a range of broad practical appeals, such as detection
of atmosphere pollutants, breath diagnostics, chemical safety, and others.
