Researchers from the University of Cambridge have seemingly achieved the impossible — they've discovered a way to observe mysterious quantum particles even without directly observing them.
How does that work? Well, first, here's a quick lesson on classical physics.
Quantum Theory
One fundamental idea in quantum theory asserts that quantum objects are able to exist in two forms: a wave and a particle, but they can't exist as one or the other until the objects are actually measured. This essentially serves as the premise behind the famous Schrödinger Cat thought experiment by Erwin Schrödinger, which involves placing a cat inside a box, closing it, then making assumptions on whether that cat is dead or alive.
But that premise, known as the wave function, has been used as more of a mathematical tool rather than a representation of quantum particles, said David Arvidsson-Shukur, a PhD student at Cambridge and the study's first author.
The researchers claim that the movements of those particles may actually be tracked without measuring them first — by examining how the particles interact with their surroundings. A paper describing the work of these researchers was published last week in the Physical Review A scientific journal.
Schrödinger's Cat: Is The Cat Dead Or Alive?
Think again of the Schrödinger's Cat thought experiment. A cat is placed inside a box that contains a flask of poison. Then, that box is sealed. At which point, the cat is either alive or dead, so long as the viewers don't actually see what's happening inside. It sounds silly, sure, but it's actually a brilliant, thought-provoking experiment that aims to discuss exactly when quantum superposition ends and reality collapses into one possibility or the other.
Here's the deal: each time a particle interacts with its environment, it leaves this sort of "tag," the researchers said. Such tags result in information being coded into the particles. The researchers formed a theory that allows them to map these tags without having to observe the particles directly.
The Forbidden Domain
The researchers discovered that the tags these particles generate by interacting with their surroundings when not under observation are directly related to the Schrödinger thought experiment. Their paper claims that "the wave function is closely related to the actual state of particles." In a sense, they've been able to explore the "forbidden domain" of quantum mechanics by tracking the movements of quantum particles even when they aren't directly observed.
So, how does this help? Well, first of all, it might help future physicists test old predictions in quantum mechanics. Such predictions include the Schrödinger's Cat experiment, or even something as advanced as the concept of telepathy, which asserts that information may be transmitted between two people without any particles traveling between them.
Of course, it could also pave the way to many discoveries down the road. The researchers' work puts quantum particles in a brand-new light, potentially helping other scientists understand their movement and behavior.
