Scheme of the demonstration of higher-order Quantum Ghost images. Picture credits: Hodgman et al. © 201
9 American Physical Society
In conventional imaging methods, a beam of photons (or other particles) is reflected from the object being imaged. Once the beam has reached a detector, the information collected there is used to create a photograph or other type of image. In an alternative imaging technique called ghost imaging, the process works a little differently: an image is reconstructed from information captured by a beam that never interacts with the object.
The key to ghost imaging is the use of two or more correlated particle beams. As a beam interacts with the object, the second beam is captured and used to reconstruct the image, although the second beam never interacts with the object. The only aspect of the first ray that is detected is the time of arrival of each photon on a separate detector. Since the two rays are correlated, the image of the object can be completely reconstructed.
While normally two beams are used in ghost imaging, recent research has shown higher order correlations, i. H. Correlations between three, four or five five rays. Higher order ghosts can improve image visibility, but have the disadvantage that higher order correlated events have a lower probability of detection, resulting in lower resolution.
In a recent work, a team of physicists from the Australian National University at Canberra has made two innovations in higher-order ghost imaging: the first demonstration of higher-order ghost imaging with massive particles (using ultracold helium atoms) and the first higher-order ghost imaging, the correlated rays used by a quantum well. As a quantum source, the researchers used two colliding Bose-Einstein condensates, which are clusters of atoms cooled to near absolute zero. At such cold temperatures, the atoms of a Bose-Einstein condensate compact and behave like a single giant atom.
In their work, the researchers experimented with correlations between up to five helium atoms. They showed that under certain conditions, higher-order ghost imaging with massive particles from a quantum source can improve the visibility of the image without affecting the resolution.
"I think the biggest importance of our work is mainly to show that such a challenging experiment is possible," said physicist Sean Hodgman of the Australian National University, first author of the work, opposite Phys.org . "In a quantum source, there are only a very small number of multi-particle correlated events, which is why some of this has not yet been demonstrated with optics, meaning that even after many tens of thousands of experimental runs, very few events are available, reconstruct a ghost."
The improvements presented here may be particularly beneficial for applications that require high visibility but are easily damaged. This is because the technique may reduce the dosage rates, thereby reducing the potential radiation damage to the sample. One such application is Atomic Spirit lithography.
"Atomic ghost lithography would be like normal atomic lithography, but the use of correlated rays would allow real-time monitoring of the lithography process," Hodgman said. "Higher order correlations would improve ghost lithography by allowing lower flows with the same signal quality, which is important because high fluxes could damage the sample."
Further work could also use higher-order quantum-ghost imaging. Perform basic quantum-mechanical tests, eg. By detecting the entanglement of several atoms or, in a similar manner, performing Bell's inequality measurements with three or more particles.
Researchers demonstrate "ghost imaging" with atoms
Sean S. Hodgman, Wei Bu, Sacha B. Mann, Roman I. Khakimov, Andrew G. Truscott. "Quantum Ghost High-order Imaging with Ultracold Atoms." Physical Review Letters
. DOI: 10.1103 / PhysRevLett.122.233601
Also on arXiv: 1901.06810 [cond-mat.quant-gas]
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Quantum Ghost Imaging Enhanced by Five-Atom Correlations (2019, June 26)
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