The shortest distance between two points is a straight line, but the shortest distance doesn’t always mean the least amount of work. What if that distance is a flat uphill or over rough terrain? If you want to get the smallest job done, a straight line may not always be your best bet. People don’t always look for the easiest way. But when it comes to natural motions in systems, one of the fundamental laws of physics says that objects will always follow the path that requires the least action. In physics, “action” is about things like energy, momentum, distance, and time.

In general, without outside interference, objects move along the path of least resistance and least change. This is called the principle of least action. We know this applies to our everyday world, and now, thanks to a new study, we know that it applies to the quantum world as well.

“A physicist’s ultimate dream is to write down the secrets of the entire universe on a small piece of paper, and the least principle of action should be on the list,” Shi-Liang, one of the project’s researchers, said in the paper. Said. “Our aim was to “see” [принцип] in a quantum experiment”.

Easier said than done. A research group from South China Normal University had to accept the fact that not only is everything in the quantum realm small and hard to see, but the movement of quantum particles is also complex, really complex. First, quantum states change when measured. On the other hand, they can only be implemented with the help of very complex mathematics.

To best describe their behavior, scientists use a combination of two things: a wave function and an emitter. Wave functions describe a particle’s state, and emitters describe how this state changes as the particle moves through the system. The problem is that wave functions and emitters are purely mathematical, and while they do a great job describing the behavior of quantum particles, they often do so using imaginary numbers. Imaginary numbers are good for math, but by definition they cannot be measured.

The team used a technique developed several years ago to circumvent this problem. In this technique, you basically reflect and filter out individual quantum particles of light called photons through a labyrinth of mirrors, crystals, and lenses. Eventually, parts of the photon’s behavior described by imaginary numbers will correspond to real measurable properties. Parts initially identified with ordinary real numbers will also be measurable, and researchers will be able to reconstruct waveforms and emitters from real measured data.

After the maze was built, the researchers combined this technique with a new one they developed to largely avoid the “quantum state change during observation” problem. They then sent photons through the labyrinth one by one and compared their behavior with the behavior predicted by the principle of least action, proving that quantum particles did indeed obey this principle, and found that reality was consistent with theory.

“The measurements in this experiment are pretty incredible and do not challenge our current understanding of quantum physics,” said Jonathan Leach, a quantum science researcher who was not involved in the study. Scientist. “It’s great to see this theory come to life in an experiment.”

There are many places where the quantum world and the everyday world do not fit. This is part of why researchers are still striving to improve the current standard model of physics. But in their desire to avoid action as much as possible, the quantum and the earthly are perfectly synchronized.