A new study involving more than 100,000 gamers from across the globe has contradicted Albert Einstein’s ideas regarding a mind-boggling phenomenon that is a cornerstone of quantum mechanics—or the physics of the very small.
The research—which was led by the Institute of Photonic Sciences in Barcelona—was conducted by an international team of physicists from 12 institutions who managed to close a loophole found in a common test of quantum mechanics.
The phenomenon in question, known as quantum entanglement, occurs when pairs, or groups, of particles interact with each other in such a way that they defy the classical laws of physics. One object can seemingly influence another simultaneously, even if they have no direct physical connection and are separated by vast distances—the length of the universe, for example.
While Einstein didn’t disagree with quantum mechanics entirely, he did find the idea of quantum entanglement to be problematic, once famously describing it as “spooky action at a distance.” He suggested this quantum behavior was impossible and that it could be explained by hidden “instructions” in the entangled particles—an argument based on two fundamental principles: locality and realism.
Locality says objects can only be influenced by causes in their immediate vicinity. (Part of this concept is that nothing can travel faster than light.) Realism, meanwhile, holds that objects in the universe have well-defined properties even when we are not looking at them—in other words, matter has a reality independent of ourselves. Together, these principles came to be known as “local realism.”
While the concepts expressed by local realism may seem natural to us, growing evidence suggests that they are incompatible with quantum mechanics. Firstly, quantum mechanics shows the simple act of observing particles in the universe can change their characteristics, thereby violating the principle of realism.
Secondly, particles that are linked or can communicate over vast distances in an instant—the “spooky action at a distance”—clearly violate the principle of locality. (In this case, some hidden form of information must be traveling faster than light between the two particles.)
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The standard way to test quantum mechanics in relation to the principle of local realism is to use something called a Bell Test, which was first developed by the CERN physicist John Stewart Bell in 1964. This is an experiment that determines whether the real-world is really as strange as quantum physics says it is. It does this by looking for the presence of “hidden” variables, that are not part of quantum theory, to explain the behavior of subatomic particles.
According to a website set up by the researchers who conducted the latest study, Bell tests involve producing a pair of entangled particles and sending them to two separated measurement stations, traditionally called “Alice” and “Bob.” (Entanglement means that their properties are strongly correlated—for example, if one particle spins left, the other must spin left, too, no matter how far away they are from each other.)
“Alice and Bob make simultaneous, unpredictable measurements on the particles,” the authors wrote on the website. “Quantum mechanics says that the measurement Alice makes will instantly influence Bob’s particle, with the effect that the measurement results agree. In local realism, this influence cannot happen, and Bob and Alice’s measurement results will often disagree. This agreement or disagreement, called correlation, is the signal that allows an experiment to decide about local realism.”
While many Bell tests over the decades have appeared to confirm the ideas of quantum mechanics over those of local realism, there is an issue here. The Bell test requires random and independently generated number sequences to determine which measurements to perform on quantum objects. But generating truly random numbers is difficult. Researchers could be influenced by unknown biases, and most computerized random number generators are not truly random, among other factors.
This flaw in the Bell test is known as the “freedom of choice” loophole—the possibility that these “hidden” variables could be influencing the experiments. This then casts doubt that the measurements are truly random, meaning it would not be possible to completely rule out the explanation offered by local realism for the behavior of any given particles.
For the new study, published in the journal Nature, the physicists enlisted more than 100,000 volunteer gamers from all around the world to try to close this loophole by generating random numbers with sheer manpower.
They were asked to play a custom-made online game called The Big Bell Quest, in which players had to tap two buttons repeatedly on a screen, representing the values one and zero. Players leveled up by creating unpredictable strings of these ones and zeros.
This provided the scientists with more than 90 million randomly human-generated binary digits, or bits—the smallest unit of computer data—which were then used in lab experiments around the world to determine how entangled particles were measured.
“People are unpredictable, and when using smartphones even more so,” Andrew White from the University of Queensland, in Australia, who was involved in the study, said in a statement.
“These random bits then determined how various entangled atoms, photons, and superconductors were measured in the experiments, closing a stubborn loophole in tests of Einstein’s principle of local realism.”
The findings of the study showed that quantum particles that are separated by large distances can still instantly affect each other, contradicting Einstein’s principle of local realism.
And because the experiment made use of so many people, the researchers can be sure that their results were precise.
“A common way to reduce the uncertainty on the result of an experiment is to repeat it many times and then check if the results are statistically significant,” they wrote on the website. “Every random number the community contributes allows the scientists to perform another run of the experiment, and to reach a more precise result. Moreover, the more different individuals are participating, the more we are assuring the statistical independence that is so important for this kind of experiments.”
Furthermore, these results resonate with those of advanced experiments conducted in 2015, in which other groups of researchers also developed loophole-free Bell tests.
But let’s not take too much away from the great German physicist. After all he did come up with the groundbreaking special theory of relativity, which revolutionized physics and transformed our understanding of the universe as we