Got a quantum problem? Throw gamers at it

A worldwide 12-hour video game session provides strong evidence to support the central tenets of quantum mechanics. Andrew Masterson reports.

100,000 people bravely volunteered to play a video game for 12 hours to help out quantum physicists.
100,000 people bravely volunteered to play a video game for 12 hours to help out quantum physicists.
Cultura RM Exclusive/Igor Emmerich/Getty Images

Human beings are pretty terrible at making up random number strands, but so are mechanical or computational random number generators – mainly because they are themselves made by the same human beings.

This is a problem for quantum mechanics researchers, who require long random number strands to rigorously test the assumptions that form the bedrock of the discipline. Now, however, a very large international team has come up with a way to overcome the limitations of machines – use humans, and lots of them.

These long strings of random numbers are critical elements of tests to determine the veracity of two ideas about physics, known as locality and realism. These tenets hold that nothing in the universe can travel faster than light and that everything has definite physical properties even if they are unmeasured.

Quantum mechanics suggests that these common-sense ideas are false, and experiments so far supported this position.

The standard way to test quantum mechanics in relation to the ideas of locality and realism is to use a Bell test – a way of seeing whether or not the real world allows the addition of “extra” or “hidden” variables not intrinsic to quantum theory in order to explain the movements of subatomic particles.

The test was first formulated in 1964 by physicist John Stewart Bell, and requires random number sequences in order to operate.

The problem, though, as noted by Bell himself, is that generating truly random numbers is challenging. Researchers may be influenced by unacknowledged bias or ambiguity in number selection, and mechanical generators may be influenced by the very hidden variables the subsequent Bell test is designed to detect.

This problem is known – with a phrasing that issues both a philosophical and mathematical challenge – as the “freedom of choice loophole”, and many scientists have spent many long hours trying to close it.

But now, the international research effort known as The BIG Bell Test Collaboration might actually have succeeded.

The organisation is dedicated to the notion of “worldwide physics experiments powered by human randomness”, and to tackle the fundamental issues of locality and realism its members turned to a resource previously little used by physicists – video-gamers.

The Collaboration secured the voluntary services of more than 100,000 gamers dotted around and the world and asked them to play a bespoke game called BIG Bell Quest. The game required players to generate unpredictable strings of ones and zeroes, and to move to ever higher levels as particular goals were reached.

Any individual player might, of course, be influenced by the very same biases, ambiguities or hidden variables that potentially bedevil quantum experiments – but these, the assumption ran, would be rendered irrelevant if random number sequences were generated simultaneously by a very, very big whack of people.

Thus, on a single day – November 30, 2016 – all 100,000 volunteers played BIG Bell Quest simultaneously for 12 hours solid. The result was an unprecedented flow of random number sequences running into the Collaboration’s server at 1000 bits per second. These were then redirected to research teams, which conducted 13 separate Bell tests, using photons, single atoms, atomic ensembles, and superconducting devices.

All up the players generated 97,347,490 binary choices.

In a letter published in the journal Nature, the Collaboration reports that the worldwide effort succeeded in closing the freedom-of-choice loophole and that the Bell test results supported the predictions of quantum mechanics. The outcomes, the authors conclude, “demonstrate global networking techniques by which hundreds of thousands of individuals can directly participate in experimental science”.

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