Quantum Particles In Motion Can Still Travel Backwards

Quantum particles have a unique ability to travel in the opposite direction from their momentum. Or, as slew (Slashdot reader #2,918) puts it, "When pushed, quantum particles can fight back." slew writes:

Who knew quantum particles were passive aggressive? It's subtle, but researchers "have shown that 'backflow' can always occur, even if a force is acting on the quantum particle while it travels. The backflow effect is the result of wave-particle duality and the probabilistic nature of quantum mechanics..."


Dr Daniela Cadamuro, Researcher at the Technical University of Munich, said "The backflow effect in quantum mechanics has been known for quite a while, but it has always been discussed in regards to 'free' quantum particles, i.e., no external forces are acting on the particle."