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Cosmic Photons Used to Test Quantum Entanglement

Category: Science & Technology
Posted: 02:01PM
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Many of the concepts in quantum mechanics seem impossible, such as entanglement where particles can have their states strongly correlated despite being separated by any arbitrary distance, so there has naturally been a lot of skepticism about their accuracy. To determine if entanglement is the result of quantum mechanics or some other local correlation, physicist John Bell developed what is called Bell's inequality a half a century ago, which allows researchers to determine if quantum mechanics can explain a strong correlation or if a loophole is a better explanation. Researchers at MIT and the University of Vienna have recently conducted an experiment that goes to a literal cosmic-extreme to all-but remove the possibility of a loophole in a quantum entanglement measurement.

The loophole that was specifically targeted is the freedom-of-choice loophole, which states that an experiment may have a bias in its setup, and that bias is what creates a correlation. There are many parts to an experiment trying to measure quantum entanglement, from the source that emits a pair of photons to the detectors that measure their properties to determine if they are correlated. One solution that has been used before is to use a random number generator to determine what properties of the photons are measured, based on a number generated in the time between the photons being produced and the detectors making the measurement. This latest experiment replaced the random number generators at the detectors with telescopes that were aimed at a star some 600 light years away. The particular star was picked because it provides a consistent stream of photons that were produced those 600 years ago and have traveled through the void and dust of space on their way to Earth all of that time.

Comparing 600 years to the microseconds involved in the experiments using random number generators results in a reduction of some 16 orders of magnitude to the loophole still being in play.

Source: MIT



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