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Are quantum jumps instantaneous?

In quantum physics, mathematically discontinuous changes – or jumps – between quantum states are popularly referred to as quantum leaps (remember the TV series). As to whether quantum leaps are instantaneous (zero time) or not – as well as random (without any harbinger) – is an open question in physics. This article below recaps additional research on the findings of Yale researchers noted in my April 2, 2020, comment on “Imaging a light pulse?”

• Scientific American > “New Views of Quantum Jumps Challenge Core Tenets of Physics” by Eleni Petrakou (December 29, 2020) – One of the most basic processes in all of nature – a subatomic particle’s transition between discrete energy states – is surprisingly complex and sometimes predictable, recent work shows.

In recent decades, however, technological advancements have allowed physicists to probe the issue more closely in carefully arranged laboratory settings. The most fundamental breakthrough arguably came in 1986, when researchers for the first time experimentally verified that quantum jumps are actual physical events that can be observed and studied. Ever since, steady technical progress has opened deeper vistas upon the mysterious phenomenon. Notably, an experiment [at Yale University] published in 2019 overturned the traditional view of quantum jumps by demonstrating that they move predictably and gradually once they start – and can even be stopped midway.

“In the end, our experiment worked, and from it one can infer that quantum jumps are random and discrete,” Minev [a researcher at the IBM Thomas J. Watson Research Center and lead author of the earlier Yale study] says. “Yet on a finer timescale, their evolution is coherent and continuous. These two seemingly opposed viewpoints coexist.”

The mystery might not just be going away, though. As Snizhko [a postdoctoral researcher now at Karlsruhe Institute of Technology in Germany] says, “I do not think that the quantum jumps problem will be resolved completely any time soon; it is too deeply ingrained in quantum theory. But by playing with different measurements and jumps, we might stumble upon something practically useful.”

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