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Physicists from the University of Gdańsk increase the accuracy of measurements

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Physicists from the University of Gdańsk are working on new theoretical mechanisms that will allow to better characterize multi-particle systems. This will increase the accuracy of physical measurements, and in the future may help build quantum computers.

Imagine playing with a cat and throwing a ball that bounces off the wall. At this point, the ball and the wall form a system that, if we want to, we can describe using physical tools. All we need is information about the parts that make up the system: ball speed, wall elasticity etc. On the other hand, once we have the information about the ball and the wall, we can reconstruct their behaviour on this basis.

Isn\'t it obvious and intuitive? Quite so. But all this changes when we go down to the level of the microcosm - the world of particles, atoms - which is the areas of interest in quantum physics.

"If we have an analogous system and we have complete information on both particles, we still can not say that we also have complete information about the whole system" - told PAP Dr. Wiesław Laskowski from the Institute of Theoretical Physics and Astrophysics, University of Gdańsk. "The quantum correlations between particles are something more than the correlations known from classical physics that describes behaviour in the macrocosm known from our daily experience. Therefore, classical theory can not describe these phenomena" - he added.

Although this observation alone is not new - it was first made by John Bell in 1964 - scientists are still working on fully understanding it and developing better methods for describing the phenomena that take place in the microcosm.

"There are no major problems if we have a system composed of a small number of particles - more specifically two. At this point, our knowledge of such systems is already very big: we can detect, measure and characterize these correlations" - said Prof. Laskowski. "Problems start when the number of particles increases, and I do not even mean that it grows to an unimaginably large value: ten particles is enough. In such case, the currently available theoretical tools are already very inefficient" - he explained.

The physicist added that it was a paradox of sorts. "A few, a dozen years ago it was quite the opposite. We had a very well developed theory, but it was difficult to observe anything in an experiment" - he said. "Now the situation has reversed. The technology has advanced so much that it is possible to observe certain quantum states that are difficult to characterize theoretically".

Prof. Laskowski is a winner of the Beethoven grant awarded by the National Science Centre, with which he will implement the project "Quantum correlations - from a few to many particles". The main objective of the research project will be to develop more efficient theoretical tools that can be used to describe correlations in multi-particle experiments. On the one hand this will allow to better understand the foundations of quantum mechanics, on the other hand it can be used for better information processing and more precise measurements. In these areas, quantum correlations are treated as a resource.

The German project partner is a group of researchers from the University of Munich, led by Prof. Harald Weinfurter. Professor Laskowski has been working with them for about 15 years. "I would say that the strongest point of this cooperation is a sort of complementarity" - the researcher told PAP. "We in Gdańsk are theoreticians, and Munich physicists are experimentalists. We want to combine these two approaches so that this theory, which our project will produce, can be immediately translated into the language of the experiment, verified and demonstrated" - he added.

"There is now a possibility of using a certain advantage of quantum correlations over classical ones" - he continued. "This is primarily the field of information processing: with the use of quantum correlations, information can be processed faster, more securely and more efficiently than with conventional methods".

Quantum correlation properties are already used in random number generators and in the creation and transmission of cryptographic keys. "They allow to generate strings of numbers that are fundamentally random, at a level unattainable with classic computer generators" - explained Prof. Laskowski.

On the other hand, in the longer run, these studies may help to realize the quantum computer project. "We still have a long way to go before we can build a purely quantum computer" - said the physicist. "Such systems are poorly resistant to environmental interference" - noted the physicist. "In our project, the term +quantum computer+ does not appear anywhere. But all the tools and ideas that will come out of this research can ultimately serve to realize the vision of such a device" - he added

author: Katarzyna Florencka

PAP - Science in Poland

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