MIT used 600 year old starlight to remove loophole in test for quantum entanglement

According to the laws of quantum mechanics, a branch of physics dealing with sub-atomic scale descriptions of the universe, quantum entanglement is a real phenomenon. In a pair of particles with identical properties, that are entangled, if an instrument is used to measure some attribute of one particle, then that instantaneously changes the attributes of the other particle, no matter how far away. Seemingly, some form of information is travelling faster than the speed of light between entangled particles. Quantum entanglement is a phenomenon that alarmed even Albert Einstein, who famously called it “spooky action at a distance”.

So far, experiments to prove quantum entanglement have not managed to convince scientists of the reality of the phenomenon. Every experiment has a number of loopholes, and non quantum factors that could explain the observations.

The best tests so far used a pair of entangled particles from the same source, and used a random number generator to specify which property should be measured at a detector. However, even such a precise experiment suffered from what is known as the ‘freedom of choice’ loophole. There is a very small chance that unknown variables or non quantum factors can affect random number generators.

Which is why, MIT scientists came up with an innovative solution for testing quantum entanglement. Instead of using a random number generator, the researchers used 600 year old starlight. There was a reference wavelength, if the measured starlight was redder than the reference frequency, then the polarisation of the particle would be read in a particular direction. If the measured starlight was bluer than the reference frequency, then the polarisation of a particle would be read in the opposite direction. Researchers essentially used photons from stars created hundreds of years before the initiation of the experiment, to decide what property of a particle would be measured.

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David Kaiser, a professor of physics at MIT said, “All previous experiments could have been subject to this weird loophole to account for the results microseconds before each experiment, versus our 600 years. So it’s a difference of a millionth of a second versus 600 years’ worth of seconds — 16 orders of magnitude. This experiment pushes back the latest time at which the conspiracy could have started. We’re saying, in order for some crazy mechanism to simulate quantum mechanics in our experiment, that mechanism had to have been in place 600 years ago to plan for our going the experiment here today, and to have sent photons of just the right messages to end up reproducing the results of quantum mechanics. So it’s very far-fetched.”

Far fetched, indeed. Skeptics have very little wiggle room left after this new experiment. Photons were fired from the University of Vienna to another University building, and the Austrian National Bank. Each site had its own detector, with an attached telescope that was watching a star 600 light years away. Photons from the star, which can be a veritable gush on clear starlit nights, were used to trigger detectors which selected which properties of the entangled photons to measure. The results were consistent with the predictions of quantum mechanics, which is that quantum entanglement is a thing, even if it is spooky.