Researchers Uncover Surprise Link between Weird Quantum
Phenomena
09 December 2010
"It would be great if we could better coordinate our actions over long distances, as it would enable us to solve many information processing tasks very efficiently. ... However, physics would be fundamentally different. If we break the uncertainty principle, there is really no telling what our world would look like."
Dr Stephanie Wehner from the Department of Computer Science and Centre for Quantum Technologies at NUS
CO-AUTHORS OF RESEARCH PAPER: Dr Stephanie Wehner from the Department of Computer Science and Centre for Quantum Technologies, NUS, with Dr Jonathan Oppenheim, Royal Society University Research Fellow at the Department of Applied Mathematics & Theoretical Physics, Cambridge University
Researchers have uncovered a fundamental link between the two defining properties of quantum physics. Dr Stephanie Wehner of Singapore's Centre for Quantum Technologies at NUS and Dr Jonathan Oppenheim of the United Kingdom's University of Cambridge published their work in the 19 November 2010 edition of the journal Science.
The result is being heralded as a dramatic breakthrough in our basic understanding of quantum mechanics and provides new clues to researchers seeking to understand the foundations of quantum theory. The result shows that two fundamental concepts in physics are linked, and addresses the question of why quantum behaviour is as weird as it is - but no weirder. The strange behaviour of quantum particles, such as atoms, electrons and the photons that make up light, has perplexed scientists for nearly a century.
One of the weird aspects of quantum theory is that it is impossible to know certain things, such as a particle's momentum and position, simultaneously. Knowledge of one of these properties affects the accuracy with which you can learn the other. This is known as the "Heisenberg Uncertainty Principle".
Another weird aspect is the concept of non-locality, which determines how well two distant parties can coordinate their actions without sending each other information. Nevertheless, it turns out that quantum mechanics allows two parties to coordinate much better than would be possible under the laws of classical physics. Einstein famously referred to this phenomenon as "spooky action at a distance".
However, quantum non-locality could be even spookier than it actually is. It's possible to imagine theories which allow distant parties to coordinate their actions much better than nature allows, while still not allowing information to travel faster than light. Nature could be weirder, and yet it isn't - quantum theory appears to impose an additional limit on the weirdness. But where does this limit come from?
The surprising result by Wehner and Oppenheim is that the uncertainty principle provides an answer. Two parties can only coordinate their actions better if they break the uncertainty principle, which imposes a strict bound on how strong non-locality can be.
"It would be great if we could better coordinate our actions over long distances, as it would enable us to solve many information processing tasks very efficiently," Wehner says. "However, physics would be fundamentally different. If we break the uncertainty principle, there is really no telling what our world would look like."
The finding bears on the deep question of what principles underlie quantum physics.
The breakthrough is future-proof, the researchers say. Scientists are still searching for a quantum theory of gravity and Wehner and Oppenheim's result concerning non-locality, uncertainty and steering applies to all possible theories - including any future replacement for quantum mechanics.