Harnessing quantum light for microscopic biomechanical imaging

The way biological materials squish or stretch reveals a lot. The stiffness of a cell wall can indicate cancer; the flexibility of a neuron unveils how brain injuries heal. One leading method of measuring such properties at a microscopic scale is called Brillouin microspectroscopy, whereby light from a laser scatters off the sample, and how that light changes after scattering indicates the sample’s properties. 

Unlike other methods, Brillouin microspectroscopy is not invasive and can perform 3D imaging of unmodified living issues, but it’s not perfect – use of high-intensity light can damage and bleach the samples. However, a new method utilizes quantum “squeezed light” to minimize damage while increasing precision and accuracy! This new method tripled samples’ survival rates, even after three hours of continuous illumination. 

What’s “squeezed light?” Well, light behaves like a wave, and quantum mechanics – more specifically, Heisenberg's uncertainty principle – dictates we can’t reduce noise in both amplitude and frequency for a single wave. If we reduce the former, the latter increases, and vice versa. Think of it like a balloon: if you squeeze it in the middle, the balloon elongates up and down; squeeze it from top and bottom, it elongates out the sides. Hence the name “squeezed light.”  

In this instance, “squeezing” the light resulted in two beams of light that were quantum-correlated. This means the beams were statistically interconnected beyond what’s normally possible. These “quantum” beams shone into the sample from opposite directions, and depending on the sample’s properties, bounced off with certain changes. By measuring these changes, researchers were able to determine important information about the sample while keeping it unharmed.

This quantum-enhanced imaging technique has countless applications from cancer biology to neuroscience. By minimizing problems with sample damage, researchers can dive deeper into the mechanics of the most miniscule realms of the human body and beyond.