Further confirmation of quantum mechanics

Quantum physics is a popular scientific discipline ¨C or so it would seem from the Big Bell Test on 30 November 2016, which involved more than 100,000 people around the world. On the day, 12 scientific institutions, including ETH Zurich, explored a question once argued over by Niels Bohr and Albert Einstein in the 1930s. The researchers have reported in the latest edition of the journal external page Nature that the experiment ¨C once again ¨C confirms Nils Bohr¡¯s point of view.

The strange quantum world

The starting point for the debate between the two famous physicists was the fact that quantum mechanics postulates phenomena that seem totally at odds with our everyday experiences. Whereas Bohr could accept the strange aspects of the quantum world, Einstein struggled with the idea that, for example, the properties of objects change as soon as the objects are observed.

In 1964, the British physicist John Bell succeeded in describing the disputed theorem, which also has philosophical relevance, in formal mathematical terms. This allowed Einstein¡¯s position ¨C that the theory of quantum mechanics is not yet complete ¨C to be tested experimentally, and a number of so-called Bell tests have been conducted over the last few decades. All of them came out in favour of Nils Bohr.

Humans instead of machines

However, physicists are stubborn, and they took issue with the fact that, so far, the experiments had failed to address an important loophole. Specifically, the test proposed by Bell requires that the measurements be carried out at random. But what happens if the machine that generates the randomness only appears to be operating at random? The result would then only appear to confirm the theory of quantum mechanics ¨C so Einstein could still have been right.

It is precisely this loophole that the Big Bell Test was now meant to close. The idea was that the randomness would no longer be generated by a machine, but rather by humans. The assumption is that, because humans are possessed of free will, they are able to generate numbers independently of one another ¨C and that, overall, these numbers will be random.

For the Big Bell Test, the researchers developed an online game that was to be played by at least 30,000 people around the world on the day of the test. During the game, the players had to come up with a random sequence of numbers ¨C the more random the sequence, the better their score in the game. The random numbers generated in this way were then used as the starting point for quantum physics experiments in the 12 participating laboratories.

Considerable outreach effect

Ultimately, more than three times the required number of people took part in the experiment ¨C a fact that, Andreas Wallraff, Professor of Solid State Matter Physics, considers a huge success. He is also delighted at the positive secondary benefit of this large-scale experiment: ¡°At the same time, the online game was an opportunity for us to bring people closer to the principles of quantum physics. So we¡¯ve made an important contribution to the goal of disseminating knowledge.¡±