Humanity is one step closer to reaching an all-encompassing ‘theory of everything’ to explain the physical universe, thanks to a new paper published in PRX Quantum.
Three scientists in the US have designed an experiment that they believe could reveal how quantum mechanics and Einstein’s General Theory of Relativity can finally agree.
Quantum mechanics explains the physics of very small things, down to the sub-atomic level, while general relativity describes the universe on the large scale and deals with the physics of space, time and gravity. However, the two theories do not match up.
“Both quantum theory and Einstein’s theory of gravity are well tested – both work exceptionally well,” co-author Dr Igor Pikovski, assistant professor of physics at Stevens Institute of Technology, New Jersey, told BBC Science Focus.
“But in modern physics, the most important challenge remains to combine these two theories into a single one. Something doesn’t seem to work, and no joint theory has succeeded so far.”
Pikovski, together with Dr Jacob Covey at the University of Illinois Urbana-Champaign and Dr Johannes Borregaard at Harvard University, designed an experiment that would uncover how the two theories may match up – something scientists have never previously managed.
The aim? To reveal how quantum effects react to the action of curved spacetime.
Curved spacetime is something that Einstein described. The theory says that gravity is the result of space and time bending around a massive object (such as a planet), and that time flows more slowly closer to the object, and more quickly further away.
The scientists designed a system of atomic clocks that can be linked together in a quantum network to reveal how they could be affected by curved spacetime.
Atomic clocks can measure time incredibly precisely. Thanks to a concept called entanglement, their quantum states can be linked together, and due to quantum superposition – a property that means systems can exist in multiple states simultaneously – the clocks can experience more than one flow of time at the same time.
By putting these clocks in different places, this quantum network could detect small differences in the movement of time caused by gravity bending spacetime.
“If performed, such a test would be the first verification of ‘quantum theory on curved spacetime’ and show how quantum systems behave even when Einstein’s gravity has to be taken into account,” said Pikovski.
This experiment would be the first step towards testing how the theories come together, but it relies on technology that we already have.
Pikovski said he hoped the paper inspired “interest and excitement about the many mysteries that nature still has to offer.”
He continued: “There is still so much we don’t know about how the world works, and corners of physics that are clouded in mystery.
“Our result shows that we can use quantum technologies to explore some of these questions for the first time in real-world experiments.”
Read more:
- Quantum science is humanity's next giant leap. Here's what that means for planet Earth
- The parallel worlds of quantum mechanics
- Quantum theory: the weird world of teleportation, tardigrades and entanglement
About our expert
Dr Igor Pikovski is the Geoffrey S. Inman '51 Assistant Professor of physics at Stevens Institute of Technology, New Jersey, US. He got his PhD in quantum mechanics from the University of Vienna in 2014. Now, he researches quantum phenomena, quantum foundations and quantum information science.
