A team of physicists from the University of Glasgow and Heriot-Watt University have found a new way to create detailed microscopic images under conditions which would cause conventional optical microscopes to fail.
They have managed to generate images by finding a new way to harness a quantum phenomenon known as Hong-Ou-Mandel (HOM) interference.
Named after the three researchers who first demonstrated it in 1987, HOM interference occurs when quantum-entangled photons are passed through a beam splitter. Inside the prism, the photons can either be reflected internally or transmitted outwards.
When the photons are identical, they will always exit the splitter in the same direction, a process known as ‘bunching’. When the entangled photons are measured using photodetectors at the end of the path of the split beam of light, a characteristic ‘dip’ in the output probability graph of the light shows that the bunched photons are reaching only one detector and not the other.
That dip is the Hong-Ou-Mandel effect, which demonstrates the perfect entanglement of two photons. It has been put to use in applications like logic gates in quantum computers, which require perfect entanglement in order to work.
It has also been used in quantum sensing by putting a transparent surface between one output of the beam splitter and the photodetector, introducing a very slight delay into the time it takes for photons to be detected. Sophisticated analysis of the delay can help reconstruct details like the thickness of surfaces.
Now, the Glasgow-led team has applied it to microscopy, using single-photon sensitive cameras to measure the bunched and anti-bunched photons and resolve microscopic images of surfaces.
They have used their setup to create high-resolution images of some clear acrylic sprayed onto a microscope slide with an average depth of 13 microns and a set of letters spelling ‘UofG’ etched onto a piece of glass at around 8 microns deep.
Their results demonstrate that it is possible to create detailed, low-noise images of surfaces with a resolution of between one and 10 microns, producing results close to that of a conventional microscope. (Phys.org)
The paper bas been published in the journal Nature Photonics.
