Quantum mechanics can be entertaining: anyone with a few minutes to spare for a video game on 30 November can do their bit to help solve a fundamental question of physics that was once argued over by Albert Einstein and Nils Bohr. ETH Professor Andreas Wallraff explains what the Big Bell Test is all about.
ETH News: Mr Wallraff, you and your laboratory are participating in the Big Bell Test. What is the purpose of the test? Andreas Wallraff: The Big Bell Test is a large-scale experiment involving 11 scientific institutions across the globe and at least 30,000 players worldwide. It is expected to provide further confirmation of quantum mechanics.
Are there still fundamental doubts regarding quantum mechanics? Quantum mechanics postulates a number of phenomena that seem very peculiar and contrary to our everyday experiences; for example, it asserts that the properties of objects change as soon as we observe them. Albert Einstein simply could not reconcile himself to this idea, whereas Nils Bohr accepted the strange behaviour. At that time, quantum mechanics was still the subject of fierce debate.
In 1964, the physicist John Bell proposed an experiment that could be used to clarify conclusively whether quantum mechanics or classical physics applies in the microscopic world of atoms and photons. This Bell Test has already been performed several times and the results have always been in favour of quantum mechanics.
So is everything settled then? Not quite. As with every experiment, the Bell Tests were based on certain assumptions, so despite the positive results some small loopholes remained. In other words, it was still possible that quantum mechanics was incomplete or even incorrect.
And the Big Bell Test will now close these loopholes? Various loopholes have already been closed in recent years; now, it should be possible to rule out another critical aspect. The basic idea of the Bell Test is as follows: if you entangle two quantum mechanical objects, such as photons, then quantum mechanics asserts that an observation of one particle can be used to conclude the state of the other particle at that moment. In the Bell Test, the two entangled particles are measured simultaneously; if quantum mechanics is correct, the measurements for the two particles will be closer to one another than would be possible under classical physics.
One important aspect of this test is that the measurements must take place on a random basis. Previously, this randomness was determined by a device also based on the principles of quantum mechanics, giving rise to a fundamental uncertainty: it is theoretically possible that the device was operating incorrectly, and accordingly the results appeared to confirm quantum mechanics. For this reason, the plan now is for humans to determine the timing of the measurements.
So can humans guarantee randomness? The fundamental assumption in the Big Bell Test is that as humans exhibit free will, they will act independently of one another to produce numbers that are random when taken as a whole.
How exactly will the experiment be conducted? On 30 November, the test subjects will play a small video game for just a few minutes on their computer or mobile phone. The players will generate a sequence of zeros and ones; this data is then transmitted to the Institute of Photonic Sciences in Barcelona and distributed to the 11 participating laboratories, where researchers will conduct the appropriate experiments. At ETH Zurich, we too will conduct experiments on the day in our laboratory, using superconducting electronic circuits as quantum mechanical objects.
What do you hope to achieve with this experiment? I would be very surprised if the results came out against quantum mechanics, so it is my expectation that the theory will once again be confirmed. Furthermore, I hope that the experiment will strengthen interest in quantum mechanics and we will be able to arouse the curiosity of as many people as possible in this area of physics. It truly is a fascinating world!
Big Bell Test – how to join in
The Big Bell Test will take place on 30 November 2016. The plan is for at least 30,000 people to play a video game or use a simple user interface in which zeros and ones are entered as quickly as possible in order to generate a random sequence of numbers, which will then be used for the experiment. Incidentally, the test’s website also provides a wealth of interesting information on the world of quantum physics.