Powerful microscopes have made a quantum leap. Using a quantum trick with light has allowed researchers to examine living cells in unprecedented detail without destroying them, a method that could improve medical diagnoses and microbiology research.
The microscopes that are generally used to examine living biological systems shine a couple of bright lights on their targets, and more powerful light sources allow researchers to start to see the cells in more detail. But this process has a fundamental limit to the precision it could achieve: at some time, a bright enough light will destroy a full time income cell.
“Our knowledge of life as it is now has relied almost completely on the grade of our microscopes,” says Warwick Bowen at the University of Queensland in Australia. “We’re really limited by technology, and it’s not apparent how to break the prevailing limits because we’ve already pushed the intensity as high as we are able to without destroying the cell.”
Bowen and his colleagues have found ways to overcome this issue. They used a kind of microscope with two laser light sources, but sent one of the beams through a exclusively designed crystal that “squeezes” the light. It can so by introducing quantum correlations in the photons – the particles of light in the laser.
The photons were coupled into correlated pairs, and some of them that had energies unlike others were discarded rather than being paired off. That process lowered the intensity of the beam while decreasing its noise, which allowed for more precise imaging.
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When the researchers tested their system, they discovered that they were in a position to make measurements which were 35 per cent sharper when compared to a similar device that didn’t use squeezed light.
“So as to achieve this kind of measurement without quantum correlations, you’d need to turn the intensity up,” says Bowen. “But if you resulted in the intensity enough to match these results, you’d destroy the sample, so we’re in a position to examine things that previously could have been impossible to see.”
These included the wall of a yeast cell ( Saccharomyces cerevisiae ), which is approximately 10 nanometres thick, in addition to the fluid within a cell, both of which would be faint even with the very best non-quantum microscopes, and completely invisible with standard microscopes. Observing these minuscule elements of living tissues could help us understand the fundamentals of life at the tiniest scales.
“This is an extremely exciting advance in the field of optical microscopy that opens the door for improving how state-of-the-art microscopes could work, at light intensities that are right at the threshold of damaging biological samples,” says Frank Vollmer at the University of Exeter in the united kingdom.
Quantum microscopes may also have practical applications, Bowen says. For instance, light-based microscopes are often used to determine if cells are cancerous or to diagnose other diseases, and squeezed light could drastically improve the sensitivity of these tests as well as speeding them up, he says.
Journal reference: Nature , DOI: 10.1038/s41586-021-03528-w
More on these topics:
- quantum mechanics
- medical technology