A new theory to test the hypotheses and methods of detecting exoplanets

Countless astrophysicists and astronomers are actively searching for unobserved celestial bodies in the universe, as the detection of these bodies could improve our understanding of space and help answer unanswered astrophysical questions. Among these elusive objects are exoplanets, planets that orbit a star other than the sun, therefore outside the solar system.

A crucial challenge hampering the detection of exoplanets is that with existing methods, it is difficult to see low emission from a secondary source that is in close proximity to a much brighter source. This considerably limits the use of direct imaging techniques in the search for exoplanets.

Researchers at the University of Sheffield in the UK and Macquarie University in Australia recently showed that it may be possible to reduce errors in detecting the presence of a weak secondary source when searching for exoplanets , especially in cases where two sources have small angular separations. Their article, published in Physical examination letters, specifically suggests that these errors could be reduced using quantum state discrimination and quantum imaging methods.

“Our work was inspired by recent papers on super-resolution quantum imaging, which was first rigorously quantified by Mankei Tsang and his colleagues at the National University of Singapore,” Zixin told Phys.org Huang, one of the researchers who conducted the study. . “These papers have shown that the angular separation of two inconsistent sources can be solved much better using quantum techniques (this is an estimation task, where the parameter we want to measure is the angular separation).”

The general idea behind the study conducted by Huang and his colleague Cosmo Lupo is that quantum techniques use the phase information contained in the optical signal. As this information is not properly exploited by direct imaging methods, quantum techniques could prove to be more efficient.

While researchers at the University of Sheffield were considering the idea for the first time, Huang watched a speculative documentary on Netflix called “Alien Worlds.” The film speculates on possible life forms that might exist on other planets and explores what they may look like.

“While watching ‘Alien Worlds’, it occurred to me that quantum techniques could be used for a quantum discrimination task, because at the end of the day, the detection of exoplanets comes down to whether we are doing the math. difference between a point and two points in the sky, “Huang explained. “With that in mind, we thought about investigating whether a quantum advantage can be obtained for a discrimination task. It turns out to be!”

Huang and Lupo applied an existing result in quantum information theory to limit the likelihood of a false negative (i.e. when an existing planet is missed by researchers). This error probability is expressed by a function called relative entropy, which is either classical or quantum. Huang and Lupo showed that the quantum relative entropy is much greater than the classical entropy.

“In other words, the information is already there in the light; we’ve just calculated the ultimate quantum limit as to how well you can do with this task,” Huang said. “We wanted to minimize false negatives, as planets are rare, and we much prefer to make a mistake in finding something rather than missing it. Hopefully we also found the corresponding metric that could achieve these probabilities. error. “

In the future, the method introduced by Huang and Lupo could serve as a benchmark for experimenters seeking to evaluate the effectiveness of existing techniques for detecting exoplanets. Additionally, it could inspire the development of alternative optical imaging tools, both for astronomical and microscopy studies.

“Our method is applicable to a wide range of wavelengths, which means that potential applications also include fluorescence microscopy, LIDAR detection and other imaging techniques,” Huang added. “We are now collaborating with Heriot-Watt University to perform an experimental proof-of-principle demonstration of the benefit discovered in the article. We will also continue to investigate how quantum can help image certain astronomical objects.”

As part of their future work, Huang and Lupo also plan to design large arrays of entanglement-compatible basic telescopes for optical imaging. Most of the existing coherent telescope arrays are based on microwave technology. However, if researchers were able to move them into the optical domain, they could potentially increase the resolution of these techniques by 3 to 5 orders of magnitude.

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