Wed. Jan 19th, 2022

Limiting quantum measurement

Despite the ambiguity of the quantum world, measurements of quantum particles give accurate results in our everyday world. How does measurement achieve this transformation? Credit: Department of Physics

The quantum world and our everyday world are very different places. In a publication published as “The Editor’s Proposal” in Physical Review A This week, UvA physicists Jasper van Wezel and Lotte Mertens and their colleagues are investigating how measuring a quantum particle transforms it into an everyday object.

Quantum mechanics is the theory that describes the smallest objects in the world around us, ranging from the constituents of individual atoms to small dust particles. This microscopic area behaves remarkably differently from our everyday experience – despite the fact that all objects in our world on a human scale are made of quantum particles themselves. This leads to intriguing physical questions: why are the quantum world and the macroscopic world so different, where is the dividing line between them, and what exactly is happening there?

Measurement problem

A special area where the distinction between quantum and classical becomes crucial is when we use an everyday object to measure a quantum system. The division between the quantum and everyday worlds then involves asking how ‘large’ the measuring device must be in order to be able to show quantum properties using a display in our everyday world. Finding out the details of the measurement, such as how many quantum particles it takes to create a unit of measurement, is called the quantum measurement problem.

As experiments examining the world of quantum mechanics become more and more advanced and involve ever larger quantum objects, one quickly approaches the invisible line where pure quantum behavior intersects in classical measurement results. In an article, UvA physicists Jasper van Wezel and Lotte Mertens and their colleagues take stock of current models trying to solve the measurement problem, and especially those who do so by proposing small modifications to the one equation that governs all quantum behavior: Schrödingers equation.

Born’s rule

The researchers show that such changes can in principle lead to consistent proposals for solving the measurement problem. However, it turns out to be difficult to create models that meet Born’s rule that tell us how to use Schr√∂dinger’s equation to predict measurement results. The researchers show that only models with sufficient mathematical complexity (in technical language: models that are non-linear and non-unitary) can give rise to Born’s rule and therefore have a chance to solve the measurement problem and teach us about it. intangible cross between quantum physics and the everyday world.

The best of both worlds: Combining classical and quantum systems to meet supercomputing requirements

More information:
Lotte Mertens et al., Inconsistency of linear dynamics and Born’s rule, Physical Review A (2021). DOI: 10.1103 / PhysRevA.104.052224

Provided by the University of Amsterdam

Citation: How the action of measuring a quantum particle transforms it into an everyday object (2021, November 30) retrieved December 1, 2021 from

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