29-May-2023: Mathematical structure of Quantum Theory reconstructed from Information Principle
Scientists have found the theoretical rationale of the mathematical structure of composite quantum systems consisting of more than one subsystem.
Quantum Mechanics, the theory that describes physical phenomena in microscopic world, was developed in the early 20th century to explain experimental observations like Black-body radiation curve, Photoelectric effect when German physicist Max Planck demonstrated through physical experiments that energy, in certain situations, can exhibit characteristics of physical matter. Later scientists like Albert Einstein, Niels Bohr, Louis de Broglie, Erwin Schrodinger, and Paul M. Dirac advanced Plank’s theory to quantum mechanics–the most accurate mathematical theory of the microscopic world. Unlike other physical theories that are built upon physically motivated postulates, Quantum Mechanics starts with abstract mathematical axioms. For instance, the second postulate of Special Theory of Relativity says that no information can travel faster than like, whereas Quantum Mechanics starts with the axiom that state of a physical system is described by a vector in complex separable Hilbert space.
Yearning for a better physical understanding, scientists are still pursuing their endeavor to re-derive the mathematical structure of quantum theory, starting with physically motivated postulates. During the last quarter of the past century, the advent of quantum information theory appends a new attitude towards this ‘reconstruction program’.
Recently, researchers from S. N. Bose National Centre for Basics Sciences, Kolkata, an autonomous institute of Department of Science and Technology, established an intriguing result in this endeavor. Dr. Manik Banik and his group took the help of a novel information principle, called the principle of Information Causality, to see what kind of descriptions are naturally disallowed for composite quantum systems (that include several quantum objects).
A recent research article published in Physical Review Letters proved that Information Causality plays a crucial role in selecting the quantum composition rule among different mathematical possibilities. In fact, Information Causality can discard a composition rule that is close to our classical worldview in the sense that the resulting theory will allow only classical-like correlations (Bell local correlations). This makes Information Causality champion over the other principles in deriving the mathematical structure of quantum mechanics. The work by Dr. Banik and his group from SNBNCBS thus brings novel physical justification towards the mathematical structure of Quantum Theory.
20-May-2023: New metric can help quantify image quality of the Sun taken from ground-based telescopes
How far have we peered into the Sun, our closest star? A new metric proposed by scientists can help quantify image quality of the Sun taken from ground-based telescopes.
Dynamic events like flares, prominences, and Coronal Mass Ejections taking place on the surface of the Sun have made the Sun the focus of interest of our astronomers, being the closest star, it can be studied in great detail, and properties of other stars may be extrapolated by the understanding of the Sun. To resolve even the smallest features in greater detail, large telescopes are built-- one of them, the 2 m National Large Solar Telescope (NLST) at Merak, being deliberated by the Indian Institute of Astrophysics (IIA).
However, there is a major disadvantage when the telescopes are on the ground. The light from the Sun passes through the Earth’s atmosphere, which is not a homogenous medium. There are random temperature fluctuations that lead to refractive index fluctuations. This causes the light to bend randomly and can be observed as the variation of intensity (scintillation/twinkling) and position of the image on the detector. One way to overcome this is to use an adaptive optics (AO) system to measure and correct for the distortions introduced by the atmosphere in real time.
But, how do we quantify the performance of our AO system or quantitatively evaluate the quality of images from ground-based telescopes? The quality of the images obtained from ground-based telescopes cannot be quantified with the Strehl ratio or other metrics used directly for nighttime astronomical telescopes.
Scientists from IIA, an autonomous institute of the Department of Science and Technology, have proposed to use a novel metric called the root mean square (rms) granulation contrast to quantify the image quality of ground-based solar telescopes.
Using theories that can be used to explain the turbulence introduced by the atmosphere, the scientists Saraswathi Kalyani Subramanian and Sridharan Rengaswamy performed simulations of how an image would look when there is no atmospheric turbulence (ideal case) and compared to the image when there is an atmosphere (perturbed image) and when AO correction is done.
They considered telescope apertures (D) that reflect the sizes of existing or planned Solar telescopes in India and around the world and determined the Strehl ratio and contrast of the granulation for various combinations of their input parameters. Since it is a simulation, the Strehl ratio can be easily determined, while in a practical system, it cannot be determined easily.
Comparing the results of the idealistic simulations to practical systems, they computed an efficiency factor deriving an efficiency of about 40 to 55% for Strehl ratio and about 50% as a lower bound for contrast. Their results will be useful in characterising the performance of any solar telescope and associated AO system.
21-Mar-2023: Asia’s largest 4-metre International Liquid Mirror Telescope inaugurated at Devasthal in Uttarakhand
Asia’s largest 4-metre International Liquid Mirror Telescope was inaugurated at Devasthal in Uttarakhand in the presence of the Governor of Uttarakhand Lt. Gen (Retd.) Gurmeet Singh.
Today's landmark event places India at a different and a much higher level of capabilities to study the mysteries of the skies and astronomy, and to share the same with the rest of the world.
Aryabhatta Research Institute of Observational Sciences (ARIES) announced that the world-class 4-metre International Liquid Mirror Telescope (ILMT) is now ready to explore the deep celestial sky. It achieved its first light in the 2nd week of May 2022. The telescope is located at an altitude of 2450 metre at the Devasthal Observatory campus of ARIES, an autonomous institute under the Department of Science and Technology (DST), Govt. of India in Nainital district, Uttarakhand
The ILMT collaboration includes researchers from ARIES in India, the University of Liège and the Royal Observatory of Belgium in Belgium, Poznan Observatory in Poland, the Ulugh Beg Astronomical Institute of the Uzbek Academy of Sciences and National University of Uzbekistan in Uzbekistan, the University of British Columbia, Laval University, the University of Montreal, the University of Toronto, York University and the University of Victoria in Canada. The telescope was designed and built by the Advanced Mechanical and Optical Systems (AMOS) Corporation and the Centre Spatial de Liège in Belgium.
The ILMT employs a 4-metre-diameter rotating mirror made up of a thin layer of liquid mercury, to collect and focus light. The metal mercury is in liquid form at room temperature and at the same time highly reflective and hence, it is ideally suited to form such a mirror. The ILMT is designed to survey the strip of the sky passing overhead each night, allowing it to detect transient or variable celestial objects such as supernovae, gravitational lenses, space debris, and asteroids.
The ILMT is the first liquid mirror telescope designed exclusively for astronomical observations and this is the largest aperture telescope available in the country at present and is also the first optical survey telescope in India. While scanning the strip of the sky every night, the telescope will generate nearly 10-15 Gigabytes of data and the wealth of ILMT generated data will permit the application of Big Data and Artificial Intelligence/Machine Learning (AI/ML) algorithms that will be implemented for classifying the objects observed with the ILMT.
The data will be analyzed quickly to discover and discern variable and transient stellar sources. The 3.6 metre DOT, with the availability of sophisticated back-end instruments, will allow rapid follow-up observations of the newly-detected transient sources with the adjacent ILMT. The data collected from the ILMT, over an operational time of 5 years, will be ideally suited to perform a deep photometric and astrometric variability survey.
There are primarily three components in a liquid mirror telescope: i) A bowl containing a reflecting liquid metal (essentially mercury), ii) an air bearing (or motor) on which the liquid mirror sits, and iii) a drive system. Liquid mirror telescopes take advantage of the fact that the surface of a rotating liquid naturally takes on a parabolic shape, which is ideal for focusing light. A scientific grade thin transparent film of mylar protects the mercury from wind. The reflected light passes through a sophisticated multi-lens optical corrector that produces sharp images over a wide field of view. A 4k ⨯ 4k CCD camera, located above the mirror at the focus, records 22 arcminute wide strips of the sky.