Quantum action occurs very, very quickly—at least 10,000 times the speed of light. That's the finding of a team of Chinese physicists who tried to measure the interaction between entangled photons, LiveScience reports. In case you don't know: "Connected" photons can be separated but still affect each other's polarization. If one is polarized "up," the other will be "down," and vice versa. Albert Einstein called it "spooky action at a distance." But how quickly does it occur?
The Chinese team measured one photon's state and waited for the "entangled state" to appear in the other—and the slowest measured speed was 10,000 times the speed of light. Not that this seems helpful in any practical way, but it does put a number on "instant" interaction. "There's a certain strain of physics that people that will say it has to be instantaneous," says a US physicist. "In fact, if it is faster than light it must be instantaneous. So if you can put a limit on it that is kind of cool."