The NIST group entangled a pair of beryllium ions in a trap, hence linking their properties, and then separated the pair and performed one of a set of possible manipulations on each ions property before estimating them. Across thousands of runs, the measurement of the pair outcomes in specific cases matched or in other cases differed more often than everyday experience would expect. Such robust correlations are hallmarks of quantum entanglement.
Moreover, statistical estimations found that the ion pairs displayed a rare high level of spookiness. “We are confident that the ions are 67% spooky,” says Ting Rei Tan, head author of the study. The studies were ‘chained’ Bell tests, implying that they were constructed from a series of possible sets of manipulations of two ions. Unlike prior studies, these were enhanced Bell tests in which the number of possible manipulations for each ion was selected randomly from sets of at least two and as many as 15 choices.
This technique produces stronger statistical results than traditional Bell tests. That is because as the total number of options expands for manipulating each ion, the probability automatically diminishes that the ions are behaving by classical or non-quantum rules. According to the classical rules, all objects must have specific local properties and can just influence each other at the speed of light or slower. Bell tests have been long employed to show that through quantum physics, objects can break one or both of the rules, illustrating spooky action.
Traditional Bell tests produce data that are a blend of spooky and local action. Perfect chained Bell tests can, in theory, prove there is zero probability of local influence. The NIST results got down to a 33% chance of local influence, less than traditional Bell tests can accomplish, although not the lowest ever reported for a chained test confirms Tan.
The NIST studies closed the direction and memory loopholes that might otherwise enable ordinary classical systems to appear spooky. The detection loophole is opened if detectors are ineffective and a subset of the data is employed to represent the entire data set. The NIST studies closed this loophole as the fluorescence identification was near 100% effective, and the measurement outcomes of every trial in each study were recorded and used to estimate results.
The NIST studies did not close the locality loophole, which is open if it is possible for the choice of settings to be communicated between the ions. To overcome this loophole, one would require separating the ions by such a big distance that communication between them would be impossible, even at night speed
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