Two contradictory versions of reality can exist at the same time, quantum experiment shows

Two versions of reality can exist at the same time, at least in the quantum world, according to a new study.

Scientists have conducted tests to demonstrate a theoretical physics question first posed as a mere thought experiment decades ago.

Within the concept, two imaginary scientists are both deemed to be correct, despite arriving at totally different conclusions.

Demonstrating this in practice therefore calls into dispute fundamental questions about physics and suggests there is no such thing as objective reality.

The results were published on arXiv, a site for research that has yet to undergo full peer review, by a British team based at Heriot-Watt University.

They set out to explore “Wigner’s friend”, named after Nobel prize-winning physicist Eugene Wigner who came up with it 1961, which is based on the idea that a photon, or a particle of light, can exist in two possible states.

According to the laws of quantum mechanics, this “superposition” means the photon’s polarisation – or the axis upon which it spins – is both vertical and horizontal at the same time.

However, once one scientist in an isolated laboratory measures the photon, they find the photon’s polarisation is fixed at either vertical or horizontal.

At the same time, for someone who is outside the laboratory and is not aware of the result, the unmeasured photon is still in a state of superposition.

Despite these apparently conflicting realities, both are correct.

In their new study, the physicists were able to bring this experiment into reality, using real photons and measuring equipment that stood in for Wigner and his “friend”.

With their results, they were able to confirm the two realities described by Wigner held true.

“You can verify both of them,” study co-author Dr Martin Ringbauer told Live Science, explaining how this bewildering concept could make the leap from theory to reality.

“Theoretical advances were needed to formulate the problem in a way that is testable,” he said.

“Then, the experimental side needed developments on the control of quantum systems to implement something like that.”

While the experiment and its results may seem a world – or even a universe – away from everyday life, it raises profound and unsettling questions for physicists about the nature of reality.

“The scientific method relies on facts, established through repeated measurements and agreed upon universally, independently of who observed them,” the team wrote in their paper.

The role of quantum mechanics is to describe the world at such a small scale that the conventional rules of physics do not apply. If measurements from this field cannot be considered absolute, it could change how the discipline operates.

“It seems that, in contrast to classical physics, measurement results cannot be considered absolute truth but must be understood relative to the observer who performed the measurement,” said Dr Ringbauer.

“The stories we tell about quantum mechanics have to adapt to that.”