High-tech experiment proves Einstein wrong
An invisible and instantaneous connection between electrons at a large distance from each other: Einstein considered such a connection to be impossible. He did not believe in 'spooky action at a distance'. In this week’s edition of Nature, FOM workgroup leader Ronald Hanson and his team have published the evidence that spooky action at a distance is indeed possible. Hanson's team realised that with electrons in two diamonds that were more than one kilometre apart from each other.
In 2014 Ronald Hanson from Delft University of Technology announced that his team was preparing a sensational quantum experiment to finally put to rest an eighty-year-old discussion in physics. The theory of quantum mechanics predicts that the observation of an object instantaneously might have consequences for another object situated further away – in theory even on the other side of the Milky Way. Albert Einstein refused to accept this phenomenon and in 1935 he called it 'spooky action at a distance'. Hanson’s team have now demonstrated that Einstein was wrong. The experiment that they carried out settles one of the most intriguing discussions in physics. In addition it has an important application: entanglement enables a form of inherently safe communication. The groundbreaking results were published in the journal Nature on 21 October 2015.
1.3 kilometres is far enough
The experiment has shown that entangled electrons in two diamonds far apart responded instantaneously to each other. In this experiment Hanson’s team did not bridge the Milky Way but the Delft University of Technology campus. Researchers used two laboratories for this, one at the Physics Building and one at the Reactor Institute, 1.3 kilometres away. The distance is large enough to prevent interaction occurring between the two setups during the experiment. PhD researcher Bas Hensen, first author of the Nature publication: "This possible exchange of information can never be faster than the speed of light. The distance between the labs is simply too large to bridge in the time needed to measure the electrons." Consequently the researchers excluded information exchange as the cause of the instantaneous reaction of the electrons.
Backdoors now closed
The interaction between electrons at a distance has been demonstrated before, but in those experiments there was still the possibility that the electrons instantaneously responded due to other causes. Physicists refer to these backdoors as loopholes. In 1964 the CERN scientist John Stewart Bell devised what he called the Bell test. In an ingenious manner this experiment measures both partners of an entangled electron pair and therefore closes all possible loopholes that could be used as an explanation. The Delft researchers satisfied the strict requirements of this Bell test with their experiment. Hensen: "It is the first Bell test free of loopholes and yet we still see that the invisible instantaneous connection due to this entanglement is real: the spooky action at a distance is genuine."
QuTech
The research of Hanson's group is cofunded by FOM, STW and NWO. Hanson's research group is part of the quantum Institute QuTech. QuTech’s aim is to develop quantum technology such as inherently safe quantum network connections and quantum computers.
Source: Delft University of Technology
More information
Contact: Prof. Ronald Hanson, +31 15 278 42 76
Links
More information, photo material and animations: http://hansonlab.tudelft.nl/loophole-free-Bell-test
https://www.youtube.com/watch?v=dKwIWIorVg8&feature=player_embedded
https://www.youtube.com/watch?v=lCfNERMPaFg&feature=player_embedded
Article in Nature
Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres