Sapphire crystal cats inspired by a famous thought experiment may help scientists discover the real reason for a mysterious boundary between the quantum and material world we all experience. 

Nobody knows why there appear to be two sets of rules for the quantum world versus the non-quantum world of classical objects we see with our eyes. While the macroscopic world of matter obeys classical physics, the microscopic world of subatomic particles follows quantum physics rules. How can the differences in these two coexisting worlds be explained? Maybe with crystal cats, as it turns out.

Putting Schrödinger’s Cat to the Test

Scientists believe they might shed light on the mystery by revisiting the famous thought experiment called Schrödinger’s Cat – but not with thoughts alone. Instead, by conducting practical experiments. Ironically, the thought experiment wasn’t originally intended to be tested scientifically. 

You probably know how the experiment goes: a cat in a box with a radioactive substance could die at any time, but it’s unknown when that would happen. By quantum physics, the cat could exist in both alive and dead states until someone opens the box. The cat’s fate depends on the moment of observation.

Many people were disturbed by the idea that particles could be in two states simultaneously. However, the dual particle, or superposition nature of particles and waves, is real. Your computer wouldn’t work unless it were true, as you can see in the video below about the Schrödinger’s Cat experiment via TED-Ed.

“An old joke says that the internet exists to allow the sharing of cat videos. At a very deep level, though, the internet owes its existence to an Austrian physicist and his imaginary cat,” says physicist Chad Orzel.

Crystal Cats Shed Light on Cat States

In 1935, Erwin Schrödinger believed the premise that a cat could exist simultaneously in both alive and dead states was absurd. Thus, it was a way to point out that people were misinterpreting quantum theory at the time. Many used the example to ridicule those who suggested that conscious observation could determine the state of matter. And they still do, worrying about “non-scientific discussions about the nature of reality, consciousness, and even Eastern mysticism.”

Nevertheless, a new study published in Science put Schrödinger’s Cat to the test. However, instead of a real cat, they used a crystal, dubbed a “Sapphire Cat” by Science News. Further, an object in two different states at once is referred to as being in a “cat state.”

The crystal cat was tiny, 16 micrograms and about the size of a grain of sand. However, for a test of quantum states, it’s considered “the fattest quantum cat to date,” reports Gizmodo. It’s several billion times heavier than an atom or molecule and visible to the naked eye.

“By putting the two oscillation states of the crystal in a superposition, we have effectively created a Schrödinger cat weighing 16 micrograms,” said lead author Yiwen Chu from ETH Zurich.

The experiment placed the Saphhire ‘cat’ in a superposition of two oscillation states, up and down. In non-technical terms, the crystal jiggled so that its atoms moved in two directions at once, capturing the spirit of Schrödinger’s Cat. Those states correspond to an alive or dead Schrödinger’s Cat. Best of all, no cat is harmed in the process. No, the crystals are not little sculptures of felines, although that would be cute.

More Than a ‘Spooky’ Thought

Thankfully, the scientists don’t plan on ever using a real cat (!), but they want to scale up the object’s mass and the distance of oscillations in its atoms. The Sapphire cat’s atoms only oscillated by the tiniest fraction of a millimeter. Still, they did, and thus show that the thought experiment is more than a strange thought. 

Similarly, three physicists won a 2022 Nobel Prize for proving that the weird world of quantum entanglement is real. Entanglement was hotly debated by Einstein, Niels Bohr, and Erwin Schrödinger in the 30s. Einstein famously thought that entanglement was absurd or “spooky action.” You still see many people mocking quantum entanglement with the phrase.

Notably, Schrödinger and Bohr were early proponents of quantum mechanics.

Related: ETs Could Communicate Across Space via Quantum Entangled Light, Suggest Scientists

Crystal Cats to Lions

The next logical step in the thought experiment gone real is moving to larger crystal cats, or maybe crystal lions? Doing so could reveal clues about the boundary between the quantum and non-quantum worlds. One of the co-authors, Matteo Fadel, from ETH Zurich, suspects gravity may play a role, as previously suggested by Roger Penrose, the founding father of quantum gravity, who also studied the quantum effects of the strange crystals long thought impossible called quasicrystals.

One day, another type of crystal, also thought impossible, called time crystals, may provide memory storage for quantum computers. These crystals’ structure repeats in time, technically existing in 4D.

Quantum Entangled Animals

Recently, another experiment used tardigrades from a gutter in Denmark to test quantum entanglement. Scientists chose them because the incredibly resilient tiny animals can survive extreme temperatures. At least one out of three withstood quantum entanglement and being frozen to a superconducting Qubit chip at near absolute zero. So we can assume they won’t be testing quantum entangled cats unless they are of the crystal variety.