01 November 2021 14:58

Relations between rays of quantum light: is everything really so entangled?

The world is on the verge of a second quantum revolution and every fundamental study is approaching a future when quantum technology will become commonplace.

One of such studies is also being developed by scientists from the Bogolyubov Institute for Theoretical Physics of the National Academy of Sciences of Ukraine and their colleagues from the Institute of Physics of the National Academy of Sciences of Ukraine.

The project is led by Andrii Semenov, who has been working on problems in the field of quantum physics for many years.

Does “spooky action at a distance” exist?

The researcher talked about the connection between distant parts of one quantum system, such as rays of quantum light, in space. Albert Einstein considered this connection as a strange and unnatural artifact of quantum theory and even called it a “spooky action at a distance.”

Real existence of this connection has been repeatedly proven experimentally and used in technology today.

Overexertion is not always necessary

The scientists working on this project with support from the NRFU are investigating this connection through theoretical means by developing alternative methods that do not require extensive experimental efforts.

During the project, the researchers plan to address three issues. Firstly, they aim to realize how to identify more general correlations between different light rays than the commonly considered Bell nonlocality . Secondly, they plan to improve the theory for quantum channels in the atmosphere and to obtain a more realistic model for them. Thirdly, they will adapt the theory of photodetection to one of the most promising light sensors used in modern quantum technologies. In particular, the grant funding has been used for purchasing a powerful computer workstation for numerical modeling. Andrii says that it works around the clock. This is not surprising, because scientists have set ambitious tasks and are actively  working on them.

Preliminary results are excellent

What has already been done in the project? Are you able to accomplish what you planned?

Andrii Semenov answered that the preliminary results are actually good. Some articles are already under review in scientific journals, others are being prepared for publication.

The researchers consider the fact that they were able to connect Bell’s nonlocality and weaker non-classical relations (correlations) clearly in one mathematical construction as a significant breakthrough. The scientists have also developed a theory for one of the most common types of photocounters – nanowire photodetectors and a powerful computer model that describes the propagation of quantum light through  the turbulent atmosphere.

Now researchers are trying to understand whether (and how) the obtained results can be applied to non-universal quantum computers.

Next year it is planned to find out if weak correlations can be used to improve quantum secure communications.

Experimentalists are confident that the results of their work will be useful in the development of the latest quantum technologies.

“Where is the button?!”

However, the project leader is rather skeptical about the possibility of creating these technologies in our country in the nearest future. Unfortunately, there are no investment opportunities for this yet.

Moreover, we have a problem not only with the development of the latest technologies, but also with the way how to use them correctly. In other words, not many people will understand how to turn on these devices and how to work with them. Scientific groups that work in this area can be counted on fingers.

Experts for the future

Andrii Semenov believes that one of the advantages of the project is the opportunity to train highly qualified professionals in a specialty that will be needed in the coming years.

He says, this is a student project because besides two young scientists there are master’s students from the Physics Department of the Taras Shevchenko National University of Kyiv who participate in it. He also emphasizes that these young people do high-quality work precisely thanks to grant funding.

Become “the worst reviewer” for yourself

By tradition, we asked the project PI what he can advise colleagues who are now applying for the NRFU calls. Andrii replied that he advises to read the terms of the competition carefully, find out all incomprehensible questions with the representatives of the Foundation and also agree the financial part of the project with the administration of the institute or university in advance.

He added that it is important to have concrete ideas and clearly defined ways of their implementation.

He always rereads his projects many times as “the pickiest reviewer”, looking for weak points. Being demanding of yourself greatly increases the chances of winning!

Svitlana GALATA

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