SPbPU: Method of quantum optical coherence tomography of vision

Main article: Vision

2023: Announcement of the method of quantum optical coherence tomography of vision

Scientists and students of St. Petersburg Polytechnic University Peter the Great have developed a method of quantum optical coherence tomography based on scanning the frequency difference of the entangled photons. This will allow, according to the researchers, to optimize the quality of images when diagnosing biological structures of internal organs by 1.5 times - doctors will be able to receive a better picture, and thanks to this, make a more accurate diagnosis and prescribe the necessary treatment. The Polytech staff published a scientific article about their theoretical research in the journal JETP Letters. This was announced on January 31, 2023 by representatives of SPBPU.

Optical coherence tomography of vision. Photo: mariupol.medkontrol.pro.

As reported, the principle of operation of optical coherence tomography is based on the interference of light scattered or reflected inside the object under study. The classic OKTAS method, which is used in medicine for January 2023, is arranged as follows: the beam emanating from the light source is divided into two, one of which passes through the object under study, reflects from tissue sections different in depth and is the basis for imaging. The second one hits the mirror, is reflected and serves as a kind of point of the report, since its parameters do not change. Then both beams hit the detector, where they are added and recorded. So the study takes place at one point - its result is the formation of a Ascan. Then, the beam passing through the object moves, and the same procedure takes place at other points in the tissue under study. Ultimately, the resulting Ascans are summed up and a two-dimensional image is formed.

Current OKTAS techniques allow images to be produced with multiple micrometer level detail. Nevertheless, at great depth, image detail deteriorates due to the dependence of the parameters of biological tissues on the wavelength of light, due to which the conditions of light interference are violated. noted Nikolai Ushakov, Candidate of Physical and Mathematical Sciences, Associate Professor of the Higher School of Applied Physics and Space Technologies, SPBPU

Polytech scientists proposed the use of matted photons and showed how to control their frequency properties to obtain the best interference conditions for pairs of photons. Thus, it is possible to obtain information on the depth at which the photon passing through the object under study is reflected, and to achieve a minimum effect of medium heterogeneity on the OKTAS of image. Thus, image detail will suffer much less than with the classical method.

A pair of photons is called confused if some of their parameters have a clear connection with each other. According to the laws of quantum physics, it is possible to describe the behavior of such a pair only by considering their joint properties. Due to this, the behavior of entangled photons during interference depends not only on their individual properties, but also on the ratio of their parameters. shared by Nikolay Ushakov

Thanks to a quantum technique, one photon from a laser pulse hits a nonlinear optical crystal, where it is split into two. At simultaneous birth, both photons have random frequencies, but from pair to pair the frequencies change in a similar manner for both photons. It was due to the controllability of the process of birth of photons that it became possible to change their properties and frequencies.

This quantum method, according to scientists, can be actually introduced into existing equipment. When compared with the classical scheme, the device of the light source changes in quantum. A nonlinear optical crystal appears in it. Scientists in the coming years plan to engage in the practical development of such a light source. Two detectors will also be needed, not one. Both should be designed to analyze single photons. The main advantage of OKTAS is that diagnosis is carried out in a non-invasive way - without penetration into tissues. Tomographs have optimal resolution and allow you to conduct a detailed study of the structures of the retina, optic nerve and choroid of the eye in real time.

This quantum OKTAS method, according to scientists, like the classical one, can be used not only in ophthalmology, but also in the fight against oncology, neurodegenerative diseases and others. In addition to medicine, experts say, modern technologies can be used to study the structure of a microelectronic board without destroying the structure.