[Reading Science] The Largest Ever 'Schrodinger's Cat' Has Appeared

Zurich Federal Institute of Technology Research Team Successfully Realizes 'Quantum Superposition State' in Reality
Sapphire Crystal Containing 10^17 Atoms Visible to the Naked Eye

The largest-ever 'Schr?dinger's cat' has appeared.

This is the evaluation of a paper on quantum phenomena published on the 21st by a research team from the Swiss Federal Institute of Technology Zurich in the international academic journal Science. The team succeeded in realizing the same quantum phenomenon as the 'Schr?dinger's cat' state?being "alive and dead at the same time"?in a solid state.

Reference photo. Photo by Pixabay

'Schr?dinger's cat' is a representative thought experiment explaining quantum mechanics. It was originally devised in the 1930s by Austrian physicist Erwin Schr?dinger to challenge quantum superposition and probability theory. Imagine placing a cat inside a box where its life or death is determined with a 50% probability. Then, is the cat currently alive or dead? Common sense says it is alive, but the quantum mechanical interpretation is that it is "both alive and dead at the same time." In other words, the state of a quantum particle is not fixed but superposed, and its state is determined probabilistically upon observation.

Of course, such superposition states and quantum phenomena occur only at the atomic scale and not at macroscopic scales like that of a cat. Scientists have been striving to realize this 'Schr?dinger's cat' thought experiment in reality. This is because it can be used as a core material for quantum computers, accelerating commercialization and enabling various applications.

There have been previous attempts, but those were at extremely small atomic scales. However, the research team succeeded in realizing such a superposition quantum phenomenon in a solid state at a size visible to the naked eye. They used a sapphire crystal weighing about half the weight of a single eyelash, 16 micrograms. The sapphire crystal, composed of approximately 10^{17} atoms, was vibrated so that the atoms simultaneously vibrated in two directions. Atoms have a fixed vibration frequency that never changes under any condition, so making them vibrate simultaneously in different directions means that the two states of the material were superposed, realizing the quantum phenomenon in practice.

This research result is particularly significant because it succeeded in a solid material about 100 trillion times larger than previous similar studies conducted at the molecular scale or below. Dr. Cheol-ki Kim of the Korea Institute of Science and Technology (KIST) said, "Materials have various states, and this means that two different motion states were superposed simultaneously in the same atoms." He added, "It has the meaning of a fundamental technology confirming that the superposition state, a core theory of quantum mechanics, actually exists. Although the research team probably considered this, there is still a long way to go before it can be used as a material for quantum computers."

Han Sang-wook, head of the Quantum Information Research Division at KIST, also said, "Generally, quantum phenomena are observed at the extremely small scale of a single atom, but the most significant point here is that the superposition phenomenon, an important characteristic of quantum mechanics, was observed in a solid system with about 10^{17} atoms." He added, "Further research is needed to maintain such superposition states for a long time and to realize entanglement, but this is an important research achievement."