The resolution of light microscopes has been vastly improved by the clever use of a common phenomenon in quantum physics.
By sending entangled light along different paths and recombining its waves, you can look at tiny objects more closely than ever before, effectively doubling the resolution without the usual complications of drastically increasing light output.
It’s accidentally called “quantitative microscopy” (QMC) and was developed by researchers at the California Institute of Technology (Caltech) in the US, who say it’s particularly suited to examining tissues and biomolecules to detect disease or study its spread.
“The combination of improved speed, improved contrast-to-noise ratio, stronger stray light protection, superior resolution, and low light intensity allows QMC to be used for dynamic imaging,” the researchers wrote in their recently published paper.
Quantum entanglement describes the associations that exist between objects that share a common history before they are discovered. And just like two store-bought shoes are connected to fit right and left feet, particles can also be connected in mathematically different ways. It’s only in a quantum system that things like shoes and electrons don’t actually go into either of those states until they’re observed. These are just opportunities that are best described as a wave.
In QMC, the particles involved were photons, or particles of light known as biphotons, once entangled in a pair.
This was done using a special type of barium beta borate (BBO) crystal. When laser light passes through a crystal, a very small fraction of photons – about one in a million – are converted into two photons. The researchers were then able to separate the biphotons again using a network of mirrors, lenses, and prisms.
One photon passes through the material under study, and the other photon is analyzed. Being entangled, the correlations measured in any photon will also tell something about the flight of its partner. This is the basis for another fairly new technique called ghost photography.
However, this intertwined double action has one more trick up its sleeve. Pivotons have twice the momentum as photons, which also means that their wavelengths are halved. Half the wavelength of light, in turn, means a higher resolution light microscope.
Light with shorter wavelengths usually carries more energy, which at some point can damage the cells under study. Think about the difference between harmless UVA rays and stronger UVB rays that can destroy DNA and cause sunburn.
In this case, although entanglement cuts the wavelength in half, it does not increase the energy of individual photons.
“Cells don’t like ultraviolet light,” says Lihong Wang, a medical engineer at the California Institute of Technology, “but if we can use 400nm light to image a cell and achieve the effect of 200nm light, which is ultraviolet light, we get ultraviolet resolution. “violet”.
There is also room for improvement in this system, including faster rendering and the ability to combine more photons, further increasing resolution. However, adding more photons means that the chance of entanglement – one in a million, really – drops even further.
Because entanglement is easily destroyed by interaction with the environment, increasing the number of photons in a system increases the chance that individual photons will interact with the environment rather than each other.
While biphoton imaging has been tried before, the researchers of the new facility have made several improvements throughout the process and field-tested it, making it one of the most promising technologies of its kind.
The study is published in the journal Nature Communications.
Source: Science Alert
