Quantum microscope uses entanglement to reveal biological structures – Physics World - physicsworld.com

The breakthrough was made by Warwick Bowen and colleagues at the University of Queensland in Australia and Germany’s University of Rostock, who showed how correlations between the detection times of photons from a bright laser could greatly improve the signal-to-noise ratio of SRS — allowing detection of molecular samples with 14% lower concentrations than were previously possible.

However, this Stokes signal is very weak, so a clever trick is used to enhance it.

A second laser at the Stokes frequency is used to illuminate the sample, which enhances the emission of Stokes photons and makes the molecular signal easier to measure.

This problem could be overcome by raising the intensities of the pump and Stokes lasers, however this would risk damaging delicate biological samples.

Overall, they achieved an improvement in signal-to-noise ratio as high as 35%, allowing them to detect molecular samples with 14% lower concentrations than were previously possible – without increased risk of laser damage.