Standard optical microscopes have surrendered their once dominant position at the forefront of scientific research to more advanced tools.
As we delve deeper into the microscopic world, photons just don’t provide enough detail when there are technologies like X-ray laser and electron microscopy available. Now a team of researchers from Hokkaido University in Japan may have found a way to use ordinary light to detect much smaller objects than has ever been possible before. The key to this technique is one of the more bizarre effects in quantum mechanics known as entanglement.
Most types of microscopy are limited by the Rayleigh diffraction limit. This principle simply states that light cannot be used to resolve a structure smaller than its own wavelength. So if you need to see something smaller than a few hundred nanometers (the shortest wavelength of visible light), a different type of electromagnetic radiation would be needed. X-ray is a popular choice as its wavelength is orders of magnitude shorter than visible light. Scientists have suspected for more than a decade that entanglement could allow photons to circumvent the Rayleigh limit, and that’s exactly what the Hokkaido University team has done.
The first step in imaging smaller objects with visible light is to generate entangled photons, which the researchers did with a special nonlinear crystal. This left them with pairs of entangled photons that were in opposite polarization states. When two particles are entangled, changes to one of them will be reflected in the other even if they are separated by incredible distances. Theoretically, these two entangled beams should be able to provide much more information about a surface.
In order to test the ability of entangled photons to increase image resolution, the team focused the entangled pairs at adjacent spots on a glass plate with a letter Q printed on it. The lettering was only 17nm taller than the surrounding plate, which should be virtually impossible to see with ordinary light. However, theentangled photons returned 1.35 times sharper images than the standard quantum limit — the lettering was completely legible.
Written By: Ryan Whitwam
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