In the 1920s, renowned physicist Albert Einstein believed he had identified a fundamental flaw within quantum physics. This led to extensive investigations revealing a pivotal aspect of quantum theory, one of its most perplexing features.
This intriguing property, known as Bell nonlocality, describes how quantum objects exhibit cooperative behavior over vast distances, challenging our intuitions. I’ve accepted this understanding for over 21 years—a remarkable insight for the 21st century.
To illustrate this phenomenon, consider two hypothetical experimenters, Alice and Bob, each possessing a pair of “entangled” particles. Entanglement enables particles to correlate, even when separated by distances that prevent any signal from transmitting between them. Yet, these correlations become apparent only through the interaction of each experimenter with their respective particles. Do these particles “know” about their correlation beforehand, or is some mysterious connection at play?
Einstein, alongside Nathan Rosen and Boris Podolsky, sought to refute this eerie connection. They proposed that certain “local hidden variables” could explain how particles understand their correlated state, making quantum physics more relatable to everyday experiences, where interactions happen at close range.
In the 1960s, physicist John Stewart Bell devised a method to empirically test these concepts. After numerous attempts, groundbreaking experiments in 2015 provided rigorous verification of Bell’s theories, earning three physicists the 2022 Nobel Prize. “This was the final nail in the coffin for these ideas,” says Marek Zhukowski from the University of Gdańsk. Researchers concluded that hidden variables could not maintain the locality of quantum physics. Jacob Valandez at Harvard University adds, “We cannot escape from non-locality.”
Embracing delocality offers substantial advantages, as noted by Ronald Hanson from Delft University of Technology, who led one of the groundbreaking experiments. For him, the focus was never on the oddities of quantum mechanics; rather, he viewed the results as a demonstration of “quantum supremacy” beyond conventional computational capabilities. This intuition proved accurate. The technology developed for the Bell Test has become a foundation for highly secure quantum cryptography.
Currently, Hanson is pioneering quantum communication networks, utilizing entangled particles to forge a near-unhackable internet of the future. Similarly, quantum computing researchers exploit entangled particles to optimize calculations. Although the implications of entanglement remain partially understood, the practical application of entangling quantum objects has transformed into a valuable technological asset, marking a significant evolution for a leading figure in discussions about the quantum nature of reality.
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Source: www.newscientist.com
