Which came first, the chicken or the egg? Both, quantum physics says

Image Credit: CC BY 2.0 Brett Jordan

Via usatoday.com by Josh Hafner

Quantum physics has an answer for the age-old conundrum: Which came first, the chicken or the egg? Possibly both.

The philosophical dilemma first posed in Ancient Greece has had biologists thinking egg. But physicists from Australia and France are looking at the riddle a different way, using it to explain their findings on how events unfold on the smallest of scales.

“The weirdness of quantum mechanics means that events can happen without a set order,” Jacqui Romero, a University of Queensland researcher, said in a statement.

Take a daily commute, she said, in which a person hops on a train before riding a bus to the office. The train ride must occur first, then the bus. That's the set order. Not so in quantum physics, Romero said.

“In our experiment, both of these events can happen first," she said. "This is called 'indefinite causal order' and it isn’t something that we can observe in our everyday life.”


Observing the "both" of indefinite causal order required researchers to employ a device called a photonic quantum switch, the university detailed in a statement. From there, tinkering with photons revealed the properties of particles to be even stranger than once thought.

As Science magazine's Adrian Cho explains, researchers discovered that "it can be impossible to say in which order two events occur, obliterating our common sense notion of before and after and, potentially, muddying the concept of causality."

And quantum physics has muddied matters before: Electrons, for example, were shown able to exist in two places at once. In a similar way, the magazine reported, a diagonally polarized photon can act in two ways at once, both events happening first.

Fabio Costa, a University of Queensland researcher on the study, said the findings could extrapolate to endeavors beyond theorizing on the chicken or the egg.

“This is just a first proof of principle," Costa said in the statement, "but on a larger scale indefinite causal order can have real practical applications, like making computers more efficient or improving communication.”

The research from the University of Queensland and NEEL Institute team published last week in "Physical Reviews Letters."

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