Quantum mechanical particles travel backwards, study confirms

July 18 (UPI) -- A team of particle physicists and mathematicians have confirmed all quantum mechanical particles move backwards -- in the opposite direction of the force acting upon them. The phenomenon is called "backflow."

Until now, scientists had only observed the counterintuitive movement among "free" quantum particles -- particles free from any active forces. In the newest experiments, researchers showed quantum particles move in reverse even when pushed by an active force.

Scientists used advanced mathematical analysis to confirm the presence of backflow. Though the phenomenon is ubiquitous, it is a very weak force and hard to measure. Small or not, understanding the effect is essential to designing technologies that take advantage of quantum mechanics.

"We have shown that backflow can always occur, even if a force is acting on the quantum particle while it travels," Henning Bostelmann, a mathematician at the University of York, said in a news release. "The backflow effect is the result of wave-particle duality and the probabilistic nature of quantum mechanics, and it is already well understood in an idealised case of force-free motion."

Researchers published their findings this week in the journal Physical Review A.

"As 'free' quantum particles are an idealized, perhaps unrealistic situation, we have shown that backflow still occurs when external forces are present. This means that external forces don't destroy the backflow effect, which is an exciting new discovery," said Daniela Cadamuro, a researcher at the Technical University of Munich. "These new findings allow us to find out the optimal configuration of a quantum particle that exhibits the maximal amount of backflow, which is important for future experimental verification."