Plotting Quantum Paths
Many systems in Nature try to achieve a low state of energy, which can be quite useful by keeping things simple. In quantum mechanics though, simple rarely happens, including when a particle in a superposition just tries to get from one point to another. Finally though, researchers at Washington University in St. Louis and University of California, Berkeley have designed and completed an experiment to actually track the path a quantum particle takes, without destroying its quantum nature.
Quantum mechanical phenomena are typically very fragile with observations causing them to collapse down to classical physics. This is true of superposition, which is the phenomenon of a particle existing in multiple mutually-exclusive states at the same time, such as being in two positions at the same time. An electron in an atom will be in just such a superposition when moving between the ground state and an excited state, as it can exist in both states at the same time, resulting in an infinite number of possible paths. Despite that, the electron will still have a desired path, like classical systems do, but observing it is tricky, as observations can collapse the superposition. The researchers got around that though by using microwave photons that would not trigger the electrons to move from one state to another. Being quantum systems, the photons would still collect information about the electrons as it passed by. The researchers also did the work with a superconducting circuit sometimes called an artificial atom, as it can have properties, like quantized electron energy levels, like atoms do.
The results confirmed the researchers' theory by showing that the electrons prefer to move along convex curves, though some had guessed other possibilities including concave curves, a straight line, and even a squiggly line. Given the amount of physics and chemistry that is the result of the behavior of electrons, this research could one day lead to some very interesting discoveries.