Quantum confusion, destroyed by quasar light



With the help of two extremely bright quasars that are more than 7 billion light-years apart, researchers have recently strengthened the issue of quantum entanglement – a phenomenon that Einstein described as "ghostly action at distance". – by eliminating one classic alternative: the freedom-of-choice mesh in the law.

Quantum compound

Of the many perplexing facets of quantum mechanics, one of the most intriguing is the idea of ​​quantum entanglement. This happens when two particles are inextricably linked, regardless of their separation from each other. Although these entangled particles are not physically connected, they can nevertheless share information immediately – seemingly breaking one of the most stubborn rules of physics: no information can be transmitted faster than the speed of light.

As far as the idea seems, quantum entanglement has been proven over and over again over the years. When researchers create two entangled particles and independently measure their properties, they find that the outcome of one measurement influences the observed properties of the other particle.

But what if the apparent relationship between particles is not due to quantum entanglement, but instead is the result of some sort of hidden, classical law of physics? In 1964 physicist John Bell approached this question by calculating a theoretical limit above which correlations can only be explained by quantum entanglement, not by classical physics. However, as is often the case, there are loopholes.

Freedom of choice?

One of the most stubborn of these loopholes is the so-called "freedom-of-choice" law in the law, suggesting that a hidden classic variable may affect how a researcher decides to intertwine apparently entangled particles. to measure. This ensures that the particles appear quantum correlated, even if they are not.

To limit the impact of the free trade zone, the authors of the new research used extremely distant quasars (exceptionally clear and energetic galactic nuclei) to decide which properties of entangled particles to measure. By allowing the light of the quasars to "choose" which properties to measure, the researchers effectively removed the model to freedom of choice from the experiment. This is because the quasars are 7.8 and 12.2 billion light-years away, so their perceived light was sent out billions of years before the researchers even came up with the experiment.

"If there is a conspiracy to simulate quantum mechanics with a mechanism that is actually classic, then that mechanism should have started working – somehow knowing exactly when, where and how this experiment would be done – at least 7 8 billion years ago, "said coauthor Alan Guth, professor of physics at MIT, in a press release." That seems incredibly unbelievable, so we have very strong evidence that quantum mechanics is the right explanation. "

According to Guth, the chance that a classic process could explain their results is about 10-20, or 1 in 100 billion billion.

"The earth is about 4.5 billion years old, so any alternative mechanism – different from quantum mechanics – that would have produced our results by abusing this loophole would have to be in place long before planet Earth" , adds -author David Kaiser of MIT. "So we have reduced all alternative explanations to very early in cosmic history."

Red versus blue

In order to carry out the research, the team used two 4-meter-wide telescopes – the William Herschel telescope and the Telescopio Nazionale Galileo – which are located on a mountain in La Palma at just over one kilometer (1 kilometer). , Spain. Both telescopes were trained on various quasars that are located billions of light years away.

Meanwhile, at a station between these two telescopes, the researchers generated pairs of seemingly entangled photons – or particles of light – and a member of each pair beamed to a detector at each telescope. As the entangled photons traveled to the detectors, the telescopes analyzed light from the quasars and determined whether the light was more red or more blue than a baseline.


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