Researchers can now spot microplastic pollution using light that never even touches the plastic samples.
March 24, 2026
Original Paper
Polymer identification via undetected photons using a low footprint nonlinear interferometer
arXiv · 2603.22253
The Takeaway
Using a quantum 'nonlinear interferometer,' this device identifies polymers by detecting near-infrared photons that are entangled with mid-infrared photons that did the actual sensing. It allows for high-speed, portable material identification without needing the expensive and bulky detectors usually required to 'see' the infrared signatures of plastics.
From the abstract
Plastic pollution has become a critical global challenge, with microplastics pervading ecosystems and entering human food chains. Effectively monitoring this widespread contamination demands rapid, reliable, and portable material identification techniques that often elude conventional Raman and FTIR spectroscopy. Undetected photon spectroscopy within a nonlinear interferometer (NLI) offers a solution, allowing the retrieval of mid-infrared absorption spectra by detecting only near-infrared signa