More than one reality can exist simultaneously at the quantum level, new experiment suggests

Researchers at the University of Innsbrück in Austria claim to have conducted an experiment proving that multiple versions of reality can exist simultaneously at the quantum level.

The experiment, known as 'Wigner's Friend', was first postulated in 1961 by Eugene Wigner, the Nobel Prize-winning physicist. It involves two individuals observing a single photon at the same time, with the photon's polarisation — the axis on which it spins — either horizontal or vertical.

However, according to the principles of quantum mechanics, the same photon - when it is not being measured in the lab - displays both polarisations simultaneously by existing in a "superposition" of two states.

In other words, the experiment proposes that it is possible that two individuals observe different states of the photon at the same time, yet their observations would be correct.

For decades, Wigner's experiment remained a theory. Recent advances in physics have enabled physicists to test Wigner's theory in labs.

"Theoretical advances were needed to formulate the problem in a way that is testable. Then, the experimental side needed developments on the control of quantum systems to implement something like that," study co-author Martin Ringbauer, a post-doctoral researcher at the University of Innsbrück, told Live Science.

In the current study, the research team created two closed labs for the experiment, with each lab having one experimenter and one friend.  

The experiment started by introducing two pairs of entangled photons with linked fates, meaning the state of one photon would tell the state of the other.

The friends, who were within the labs, observed one photon (from the pair) in their lab and recorded their observations. The process was repeated for the second photon also.

When friends observed the photons, they found them to be in a state of polarisation.

But when the photons were observed from outside the closed labs using interference experiments, they were found to be in a state of superposition (entangled state).

When Wigner originally introduced the idea in 1961, only one scenario was used in the experiment. But, with the new experiment, the observations were doubled, and the team found that the results described by Wigner still held.

According to the research team, the observations made by the experimenters about the photons were correct and provable, but they were different from the measurements of their friends — which were also correct and verifiable.

The findings of the study were published in the journal arXiv.

Further reading

China details its quantum key distribution network

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• 22 January 2018

All-photonic quantum repeaters could pave the way for faster, more secure quantum internet

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• 06 February 2019

Scientists claim major quantum computing milestone after getting two silicon qubits to communicate with each other

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• 07 March 2018

IBM launches world's first commercial quantum computer

• Hardware
• 08 January 2019

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• Topics
• Communications
• Eugene Wigner
• quantum mechanics
• Wigner's friend