# Researchers describe the wavefunction of Schroedinger's cat

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 precise measurements, 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 quantum physics, the cat is described by the quantum wavefunction.

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 quantum mechanics, 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?"

This debate has remained purely theoretical for decades, until three teams of quantum theorists—including co-authors Dr Cyril Branciard and Dr Eric Cavalcanti—recently proposed experimental tests to answer this question.

"The new approach tests whether the competing interpretations of the wavefunction can explain why we cannot tell quantum states apart with certainty, which is a central feature of quantum mechanics," says lead author Mr Martin Ringbauer.

"Our results suggest that, if there is objective reality, the wavefunction corresponds to this reality."

In other words, Schrödinger's cat really is in a state of being both alive and dead.

As measurements improve further, physicists will be left with two possible interpretations of the wavefunction: either the wavefunction is completely real, or nothing is.

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**More information:**"Measurements on the reality of the wavefunction."

*Nature Physics*(2015) DOI: 10.1038/nphys3233

**Citation**: Researchers describe the wavefunction of Schroedinger's cat (2015, February 3) retrieved 25 August 2019 from https://phys.org/news/2015-02-wavefunction-schroedinger-cat.html

## User comments

aromrussell_russellSoylentGrinIf you're in the universe where the hammer falls, you'd hear "ouch!". If you're not, you'd hear silence. It would be a very boring experiment that would just tell you and the subject which branch your reference frame took.

antialias_physorgLook up the "Wiegner's friend" thought experiment (extension to the Schrödinger's cat experiment)...if you do it on wikipedia pay attention to the "criticism" section.

IronhorseALosikrufusgwarren1. Defines potentiality vs actuality

2. Defines potential energy vs kinetic energy

Mostly described by statistical functions using the physic. Problem is, there's more discussion about what we are "looking for" and "what we find." First you must limit the set to only possibilities, but then you would would need some sort of tool to help define "possibility". Hence, an "event" exist or does not exist might have some meaning when quantified and qualified, but if it something you have no idea of wither ... arguing over the later seems redundant.

rufusgwarrenrufusgwarrenrufusgwarrenrufusgwarrenthingumbobesquireandy_barrette_5Spaced out EngineerMy question is, if the waveform actually exists then what about this study? http://m.phys.org/news/2014-12-quantum-physics-complicated.html

In this article it was claimed that the duality nature was just another aspect of uncertainty. So is uncertainty a waveform that appears as duality? Or does the waveform appear as uncertainty from a instrumentalist perspective? I'm curious what the new infermometers will tell us. http://m.phys.org/news/2014-12-team-aharonov-bohm-interferometer-band-topology.html

https://journals....0.063630

Spaced out EngineerI meant this aps.org link. I can't believe they maybe able to go beyond the limit. The other spooky thing is the information density as well as the weak measurement. I may live to see the day statistics and mathematics find real interoperability rather than theortically overlay and exchange! Then again I am uncertain about the reals, however optimistic to the integers within the Laglands program. ;)

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