Fundamentally strange in nature, quantum physics requires metaphors like spinning coins and thought experiments with hidden cats in boxes for us to even begin to understand its laws.
However, even in the more obvious realm of classical physics, nuances of quantum behavior can be portrayed through rather straightforward scenarios. Scientists have found that the behavior of microscopic oil droplets going down two neighboring tubes in a bath of vibrating fluid is consistent with a well-known quantum thought experiment.
“It turns out that this hydrodynamic pilot-wave experiment exhibits many features of quantum systems which were previously thought to be impossible to understand from a classical perspective,” says Massachusetts Institute of Technology (MIT) fluid dynamicist John Bush.
Bush and MIT physicist Valeri Frumkin imitated the Elitzur-Vaidman bomb tester, a well-known example of an interaction-free measurement system that allows one object’s quantum state to be determined by gently caressing the wave of another object, without upsetting the delicate nature of either.
Although the method has been used with low-intensity imaging equipment, no one is sure what is meant by “interaction-free” in terms of physical definition. A photon is instantaneously split into two states (a superposition) in the bomb tester experiment. These two states move along one of two channels, and one of those channels contains a “bomb” half the time. A “bomb” is a metaphor for an entity that can disrupt the superposition by absorbing a photon and destroying its own quantum state in the process.
If a photon leaves the system, it probably avoided any explosives. Now, the beauty of quantum physics is that, without ever “detonating” the bomb, the state of the split photon when it is recombined into a single whole can also reveal whether or not the bomb was present. This is true even when the photon took the other channel. From the perspective of classical physics, this is incomprehensible, which is why quantum physics was developed. To put it simply, the bomb tampers with the photon’s superposition-generated probability. When the photon’s wave-like properties are measured at the end, that interference can be found.
Therefore, it is unexpected that this study’s conventional setup yielded the same outcome. Instead of photons, droplets formed liquid ripples that behaved like superposition possibilities. If the expanding ripples collide with the bomb, the droplet will be impacted even if it took the other channel when the two channels combine again.
In a technical sense, the experiment is more similar to the interpretation of quantum experiments known as pilot-wave theory, which holds that the properties of an item are guided by interacting ripples carrying little surfing particles. The Elitzur-Vaidman bomb tester and the traditional experiment matched statistically. It demonstrates a link between the more ambiguous and uncertain quantum world and the more defined and solid world of classical physics, according to the researchers.
The reason why quantum behaviors such as waves of possibility seem to ‘collapse’ into discrete states is better understood in light of this. “Here we have a classical system that gives the same statistics as arises in the quantum bomb test, which is considered one of the wonders of the quantum world,” Bush states. As it turns out, the phenomenon is not as amazing as we first thought. And here’s another instance of quantum activity that makes sense when viewed through the lens of local realism.”