Schrödinger's cat highlights a long-standing dilemma in quantum mechanics: is the cat really alive and dead, or is the weirdness just in our head?

Researchers at The University of Queensland have now made major progress in answering this question.

Using four-dimensional states of photons, and subjecting them to very , they ruled out the popular view that describing the cat as dead and alive is just due to a lack of knowledge about its real state.

As with all objects in , the cat is described by the quantum .

Dr Alessandro Fedrizzi, from the UQ School of Mathematics and Physics, explains that although the quantum wavefunction is our central tool for describing physical systems in , it is still unclear what it actually is.

"Does it only represent our limited knowledge about the real state of a system, or is it in direct correspondence with this reality?

"And is there any objective reality at all?"

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