Sat. May 21st, 2022

A new theory for testing hypotheses and methods for detecting the exoplanet

An optical imaging system (modeled as a thin lens) is used to distinguish between two hypotheses. Hypothesis H0: only the star is present. Hypothesis H1: there is a star-planetary system present where the planet has much weaker intensity relative to the star. Credit: Huang & Lupo.

Countless astrophysicists and astronomers are actively searching for unobserved celestial bodies in the universe, as the discovery of these bodies can improve our understanding of space and help solve unanswered astrophysical questions. Among these elusive objects are exoplanets, planets orbiting a star other than the sun, ie outside the solar system.

A crucial challenge that prevents the detection of exoplanets is that with existing methods, it is difficult to see weak emissions of a secondary source that is near a much brighter source. This significantly limits the use of direct imaging techniques in exoplanet searches.

Researchers at the University of Sheffield in the United Kingdom and Macquarie University in Australia have recently shown that it may be possible to reduce errors by detecting the presence of a weak secondary source during exoplanet searches, especially in cases where two sources have small angular separations. Their paper, published in Physical review letters, specifically suggests that these errors could be reduced by quantum state discrimination and quantum imaging methods.

“Our work was inspired by recent articles on super-soluble quantum imaging, which were first accurately quantified by Mankei Tsang and his colleagues at the National University of Singapore,” Zixin Huang, one of the researchers who conducted the study, told “These papers showed that the angular separation of two incoherent 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 her colleague Cosmo Lupo is that quantum techniques use the phase information contained in the optical signal. Since this information is not properly utilized by direct imaging methods, quantum techniques may prove to be more effective.

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

A new theory for testing hypotheses and methods for detecting the exoplanet

The optimal measurement that achieves the optimal error probabilities, within the limit that the two sources are very close to each other. It is a multimode waveguide that can be used as a spatial state sorter. Photo counting is performed at the exit. Credit: Huang & Lupo.

“While watching ‘Alien Worlds’, it occurred to me that quantum techniques could be used for a quantum discrimination task, as it is ultimately the discovery of exoplanets that involves whether we tell the difference between a place and two spots. in the sky, “Huang explained. “With this in mind, we thought about investigating whether a quantum advantage can be achieved for a discrimination task. It turns out that it can!”

Huang and Lupo used an existing result in quantum information theory to limit the likelihood of a false negative (i.e., when an existing planet is missing by scientists). Such a probability of error is expressed by a function called the relative entropy, which is either classical or quantum. Huang and Lupo showed that the quantum relative entropy is much larger than the classical one.

“In other words, the information is already there in the light; we have simply calculated the ultimate quantum limit for how well you can handle this task,” Huang said. “We wanted to minimize false negatives, because planets are rare, and we would much rather make a mistake by finding something rather than missing it. With a little luck, we also found the matching measurement that could achieve these error probabilities.”

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

“Our method applies to a wide range of wavelengths, which means that the potential applications also include fluorescence microscopy, LIDAR detection and other imaging techniques,” Huang added. “We are now collaborating with Heriot-Watt University to conduct a principally proven experimental demonstration of the benefit discovered in the newspaper. We will also continue to investigate what capacity quantum can help depict certain astronomical objects.”

As part of their future work, Huang and Lupo also plan to design large baseline, entangled telescopic arrays for optical imaging. Most existing cohesive telescopic arrays are based on microwave technology. However, if the researchers were able to move these into the optical domain, they could potentially increase the resolution of this technique by 3 to 5 orders of magnitude.

The best of both worlds: Combination of classic and quantum systems to meet supercomputing requirements

More information:
Zixin Huang et al., Quantum Hypothesis Testing for Exoplanet Detection, Physical review letters (2021). DOI: 10.1103 / physrevlett.127.130502

Mankei Tsang et al., Quantum Theory of Superresolution for Two Incoherent Optical Point Sources, Physical review X (2016). DOI: 10.1103 / PhysRevX.6.031033

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