‘Mind-blowing’ quantum twin paradox experiment could make better GPS

15 Oct 2019

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An experiment using lasers to test Einstein’s so-called ‘twin paradox’ could help find a way to make more accurate GPS.

A scientific theory proposed by Albert Einstein and featured in the sci-fi blockbuster Interstellar could soon be put to the test and potentially make GPS and autonomous cars a lot more accurate.

An international team of researchers, led by Dr Magdalena Zych of the University of Queensland, has published a study to Science Advances putting down its aim to test the so-called ‘twin paradox’ using quantum particles in a superposition state.

According to Zych, the paradox is one of the most counterintuitive predictions in relative theory as it says that time passes differently for people at different distances based on how far away they are from an enormous mass. The same applies for when two people are travelling at different velocities.

“When the twins reunite, the travelling twin would be much younger, as different amounts of time have passed for each of them,” Zych said.

“It’s a mind-blowing effect – featured in popular movies like Interstellar – but it’s also been verified by real-world experiments, and is even taken into consideration in order for everyday GPS technology to work.”

The ‘Holy Grail’ of theoretical physics

As part of this study, the team found that advanced laser technology could be used to realise a quantum version of the twin paradox. In the quantum version of the experiment, the twins would be reduced to one particle travelling in a quantum superposition.

In effect, the particle is in two places at the same time, different to placing the particle in one or two locations randomly. The particle will exist in superposition with two trajectories and different speeds, with the aim of seeing if a different amount of time passes for each of them – as proposed by the twin paradox.

“If our understanding of quantum theory and relativity is right, when the superposed trajectories meet, the quantum traveller will be in superposition of being older and younger than itself,” Zych said.

“This would leave an unmistakeable signature in the results of the experiment, and that’s what we hope will be found when the experiment is realised in the future.”

Such a discovery would allow physicists make more precise sensors and clocks for use in future navigation systems, autonomous vehicles and earthquake early-warning systems. Not only that, but it could be a major leap forward in our understanding of physics.

“A key example is, can time display quantum behaviour or is it fundamentally classical?” Zych added.

“This question is likely crucial for the ‘holy grail’ of theoretical physics: finding a joint theory of quantum and gravitational phenomena.”

Colm Gorey was a senior journalist with Silicon Republic