The concept of force is one of the most basic ideas you learn as a child – pushing an object makes it go away from you. So imagine what it would be like if you nudged a ball forward and see it it roll back up instead. This sums up the new discovery on quantum particle behavior made by researchers at the Universities of York, Munich and Cardiff – so it’s quite understandable how intriguing and probably unreal it might sound. However, to mathematicians devoting their life’s work to quantum mechanics, this could have registered just a mild surprise. After all, quantum particles have been defying the laws of physics from the start. Take for example superposition of states in quantum mechanics where particles are thought of as existing across all the possible states at the same time until measurement is made. In the same way, the discovery that applying a directional force to quantum particles can cause movement in the opposite direction may sound like science fiction, but can be mathematically explained.
Initially, what is called as the “backflow effect” in quantum mechanics was thought to be only possible to “free” quantum particles. Dr Henning Bostelmann, one of the researchers from York’s Department of Mathematics explained that “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,” which simply meant as having no external force, whether reflections or transmission, applied to them. There has never been any previous indication that quantum particles have the ability to partially reverse its direction opposite to its momentum, the very definition that gained the term “backflow effect” for this unique property of quantum particles.
But recent analytical and numerical investigations were conducted to specifically measure the presence of the backflow effect and prove its presence even as the quantum particles are influenced by an external force. The research yielded positive results. It showed that while forces such as reflection can make the particles go backward and increase backflow, their experiments also proved that backflow effect, though in small measure, is still present even in the absence of reflection. The minimal extent to which this effect is present is probably why it was never identified until recently. However, it is still an important breakthrough because it will make a significant change in the way results of experiments with quantum particles will be handled.
This new discovery is considered as a huge breakthrough in the field of quantum mechanics. Interpretation of research will now have to factor in the effect of constant backflow to the behavior of quantum particles. It will also reduce the degree of error and fine-tune calculations of future quantum experiments as well as set optimal configuration for quantum particles that exhibit maximized backflow behavior that will increase the integrity of future experimental verification. As mentioned, these new findings will play a significant role in the application of quantum mechanics as they will undoubtedly advance quantum technology in different fields, including data transfer encryption and computer security.