What is really happening at the quantum level? The new version of a classic experiment lately found that particles at this level can be seen behaving something like billiard balls that roll about a table, but in a rather "surrealistic" fashion.
The results kind of challenge the standard interpretation of quantum mechanics.
The team of Aephraim Steinberg, a physicist from the University of Toronto and a senior fellow of the Canadian Institute for Advanced Research (CIFAR), conducted a new version of quantum mechanics' most famous experiment. This is where photons or particles of light are fired at two slits prior to being detected on a screen.
For decades, physicists believed it would never be known which slit a specific photon went through, as any measurement stops it and disturbs the system. In 2011, Steinberg's team successfully tracked the photons' trajectories through "weak" measurements that barely disturb the particles - a method that demonstrated trajectories looking similar to classical ones or those of balls that fly through the air.
The results appeared to be aligned with the De Broglie-Bohm theory, which some physicists criticized for its failure to explain entanglement, where two photons are so closely connected that measurement on one instantly affects the other no matter their distance.
"I'm less interested in focusing on the philosophical question of what's 'really' out there," says Steinberg of the varying interpretations of quantum mechanics. "Rather than thinking about different metaphysical interpretations, I would phrase it in terms of having different pictures, [which] can help shape better intuitions."
According to critics, measuring one particle would sometimes lead to an inaccurate prediction of the entangled particle's trajectory, or what they dubbed as "surreal trajectories."
The team experiment now showed that the surreal action is a mere consequence of non-locality, or the particles' ability to influence each other instantly even at a distance. The "incorrect" predictions of entangled photon's trajectories, the team stated, actually resulted from where in their track the entangled particles were measured.
Both particles considered, the measurements added up and remained consistent with real trajectories.
The authors pointed out that this validates both standard and non-standard interpretation - the De Broglie-Bohm theory - and makes them "mathematically equivalent."
The De Broglie-Bohm theory was first proposed by Louis de Broglie in 1927, an interpretation that treats quantum objects as classical particles but considers the riding on top of what is called as a pilot wave. While probabilistic, the particle indeed takes a real trajectory from source to target - not simply collapsing into a specific location once measured.
Physicist Howard Wiseman of Griffith University, who proposed the experiment, echoed that the results bolstered the pilot-wave interpretation. "[It's] something that's not recognised by a large part of the physics community."
The findings were published in the journal Science Advances.