Increase dirt by fifty times and suddenly it no longer seems to play by the same rules. Its contours, for example, will not look well defined most of the time and will resemble a diffuse, scattered cloud. This is the weird sphere of quantum mechanics. "In some books you will find that they say that a particle is in different places at once," says physicist Marcus Arnd of the University of Vienna in Austria. "Whether this really happens is a matter of interpretation."
Another way: Quantum particles sometimes act as waves propagating in space. They can bump into each other and even come back on themselves. But if you click on this wavy object with certain tools, or if the object interacts in specific ways with close particles, it loses its properties as a wave and begins to act as a discrete point ̵
But at what size does quantum effects no longer apply? How big can something be and still behave like a particle and a wave? Physicists tried to answer this question because experiments were almost impossible to design.
Now Arndt and his team have overcome these challenges and observed properties similar to quantum waves in the largest objects so far – molecules composed of 2000 atoms, the size of some proteins. The size of these molecules beat the previous record twice and a half. To see this, they inject the molecules into a 5-meter tube. When particles hit a target at the end, they don't just land as randomly scattered dots. Instead, they formed an interference pattern, a strip of dark and light stripes, suggesting waves collide and combine with one another. They published today the work in Natural Physics .
"Surprisingly, this works in the first place," says Timothy Kovachi of Northwestern University, who did not participate in the experiment. It is extremely difficult to experiment, he says, because quantum objects are delicate, suddenly moving from their undulating state to particles such as interacting with their environment. The larger the object, the more likely it is to knock on something, heat it or even break it, which triggers these transitions. To keep the molecules in a wavy state, the team clears a narrow path for them through the tube, taking police boundaries off the parade route. They keep the pipe in a vacuum and prevent the entire tool from shaking even the smallest piece using a system of springs and brakes. Then the physicists had to carefully control the speed of the molecules so that they did not heat up too much. "It's really impressive," Kovachi says.