Strange behavior of light particles challenges quantum theory
At the super-small level of all things quantum, most bets are off in terms of the rules of normal physics. Still, there are some behaviors in this arena that researchers felt they could count on – such as the way entangled photons operate. But new research out of the University of East Anglia (UEA) in the UK has now shown that even those tiny particles of light don't behave as we previously thought.
The UEA team was researching a process called spontaneous parametric down-conversion (SPDC), in which a beam of photons is passed through a crystal to create entangled photon pairs. When photons are entangled, their behaviors remained linked, even if they become separated.
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"Photons pairs are entangled in a specific quantum sense," David Andrews a professor in UEA's School of Chemistry, told New Atlas. "Like twins born conjoined, the information in either of them is inextricably associated with the information in the other – even when they are separated."
And while those entangled photons can separate after they emerge from the crystal, the thinking has always been that they originate from one single point inside the crystal. The new research has shown that they can actually be generated from different parts of the crystal.
"The paired photons can emerge with separations in their origin of hundredths of a micron – despite being entangled, it is as if they were not even born close together in terms of atomic dimensions," Andrews told us.
Trapping and manipulating photons is one of the key elements of quantum computers, machines that could potentially perform hundreds of times more calculations per second than current computers. So learning that entangled photons don't quite enter the world the way previously thought could have an impact on the design of future systems. Andrews says the finding injects a new level of uncertainty into the operation of quantum components.
"Everything has a certain quantum 'fuzziness' to it, and photons are not the hard little bullets of light that are popularly imagined," he said in a statement.
The work of the researchers has been published in the journal Physical Review Letters.