Physicists have discovered surprising quantum-like behavior in tiny bouncing droplets
Quantum physics is so fundamentally strange that we need thought experiments of cats in boxes and coin metaphors to even begin to understand its laws.
However, even in our classical world, where physics is more intuitive, shades of quantum behavior can be represented using relatively simple scenarios.
Researchers who conducted experiments on tiny droplets of oil flowing through two adjacent channels in a basin of vibrating liquid discovered that the behavior of the droplets matches a famous quantum thought experiment.
“It turns out that this experimental hydrodynamic wave experiment shows many features of quantum systems that were previously thought impossible to understand from a classical perspective,” says John Bush, a fluid dynamics scientist at the Massachusetts Institute of Technology (MIT).
Bush and his colleague, Valery Frumkin, a physicist at the Massachusetts Institute of Technology, simulated the Elitzur-Wiedemann bomb tester — a well-known example of interaction-free measurement — where they were able to extract details about the quantum state of one object using the gentle caress of another object’s wave without disturbing either of them. . Sensitive nature.
This approach has been applied to low-density imaging technology, although despite its uses, there is no consensus on what “interaction free” physically means.
In a bomb test experiment, a photon splits into two states simultaneously (superposition). These two states travel through one of two channels, and half the time, one of those channels contains a “bomb” — an analogy of an object that can destroy superposition by absorbing a photon and destroying its quantum state in the process
If a photon exited the system, it probably didn’t hit any bombs. Now the magic of quantum physics is that the state of the split photon when it reassembles into a single whole can also tell us whether the bomb was there or not – even when the photon took the other channel – without ever “detonating” the bomb.
This doesn’t make sense from the point of view of classical physics, but that’s why we have quantum physics. In basic terms, the bomb interferes with the probabilities that superposition creates for the photon. This interference can be detected when the wave nature of the photon is finally measured.
It is therefore surprising to find the same result in this study in a classical setting.
The droplets replaced the photons, and the liquid ripples they created served as superposition possibilities—if those expanding ripples hit the bomb, it affected the droplet when the two channels merged again, even if the droplet itself took the other channel.
Technically, this experiment shares an explanation of quantum experiments called pilot wave theory, in which interacting ripples carried by tiny surfing particles direct the properties of an object.
Statistically, the classic experiment matched the Elitzur-Weidmann bomb tester. Researchers say it shows a bridge between the static and rigid world of classical physics and the more mysterious and less certain quantum world.
This helps us understand more about why quantum behaviors, such as probability waves, “collapse” into discrete states.
“Here we have a classical system that produces the same statistics as a quantum bomb test, which is one of the wonders of the quantum world,” Bush says.
“In fact, we find that this phenomenon is not so remarkable at all. This is another example of quantum behavior that can be understood from a local, realistic perspective.”
The research was published in Physical review a.