It's time to put all the quantum cards on the table. That’s the view of a group of physicists who assembled in Vienna last month to present a variety of ideas, results and plans for future experiments that might help find an explanation for the weirdness of quantum theory.
Quantum physics is well known for being weird. The theory – and the experiments that have confirmed it – rip gaping holes in our concept of space, time and reality. Most physicists simply accept this as the way things are. But most of the 70 or so researchers who gathered in Austria at the Vienna symposium on “Emergent Quantum Mechanics” from 23 to 25 October were there to go deeper, and ask where the quantum laws might come from. Is quantum physics a stepping stone to a deeper understanding of reality?
“There are many people who think they are well along the path to a better understanding, but they all contradict each other,” says Aephraim Steinberg of the University of Toronto, Canada. “So maybe one of them is right – but I certainly don’t know which one.”
Steinberg presented experiments that attempt to show the paths photons take as they appear to pass simultaneously through two slits. This is because of quantum superposition – a trick in which the photon seem to be in two different states at once. The most widely accepted interpretation of quantum theory claims that this is possible because the photons only have definite properties once they have been detected. Before that, there is only a mathematical wave function describing possible outcomes of the measurement.
But Steinberg prefers to interpret the experiment in terms of so-called Bohmian mechanics, which suggests that there are pre-existing connections between all quantum particles. Each particle has an associated “pilot wave” that guides its position and momentum, so it takes a particular trajectory through the double slits. “These are very straightforward experiments that draw a connection between that model and what happens in the real world,” he says.
Many find Bohmian mechanics unsatisfactory. But discussions at the meeting made it clear that the same can be said of most interpretations – and it was.
To read more, click here.