"This Sentence happily existed in all possible states before you observed it. Now it has collapsed into a single state. I hope you are satisfied."

The Idea behind this one is a little (HUGE) part of quantum physics called Quantum entanglement, where pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently—instead, a quantum state may be given for the system as a whole. If you observe one particle, the other one will become the exact same.

Now yes I know some other Fiz-x students have done blogs about this, but I found an amazing experiment that helps to show this entanglement.

Conventional imaging devices like cameras and x-ray machines create pictures by detecting photons that interact with the things being imaged. Now researchers have developed a new quantum imaging technique that shines a beam of photons on an object but then, instead of using these photons to form a picture, uses instead a completely different beam that has never come near the object. If this sounds a bit spooky, it is: what connects the two sets of photons and allows this technique to work is the bizarre quantum physics phenomenon known as entanglement. The advantage of a quantum entanglement camera like this is that you can illuminate an object using photons with a certain wavelength and then use entangled photons with a different wavelength to form the image.

In the experiment, there are two paths down which a photon can travel. Each contains a crystal that turns the particle into a pair of entangled photons. But only one path contains the object to be imaged.

According to the laws of quantum physics, if no one detects which path a photon took, the particle effectively has taken both routes, and a photon pair is created in each path at once.

In the first path, one photon in the pair passes through the object to be imaged, and the other does not. The photon that passed through the object is then recombined with its other ‘possible self’ — which traveled down the second path and not through the object — and is thrown away. The remaining photon from the second path is also reunited with itself from the first path and directed towards a camera, where it is used to build the image, despite having never interacted with the object.

A cardboard cut-out of a cat imaged by photons that never went through the cut-out itself.

The researchers imaged a cut-out of a cat, a few millimeters wide, as well as other shapes etched into silicon. The team probed the cat cut-out using a wavelength of light which they knew could not be detected by their camera. The cat was picked in honor of a thought experiment, proposed in 1935 by the Austrian physicist Erwin Schrödinger, in which a hypothetical cat in a box is both alive and dead, as long as no one knows whether or not a poison in the box has been released. In a similar way, in the latest experiment, as long as there is nothing to say which path the photon took, one of the photons in the pair that is subsequently created has both gone and not gone through the object.

So as you see, Quantum Entanglement is cool, and we are actually able to see it with our own eyes, aided with special instruments of course. So in conclusion, if you ever see a cat, put it in a box, it makes for a fun experiment.