Researchers describe the wavefunction of Schroedinger's cat

February 3, 2015
Looking underneath the wavefunction — represented by the Greek letter “psi” — in the search for quantum reality. Credit: Benjamin Duffus and Martin Ringbauer

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?"

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.

Explore further: Searching for quantum physics in all the right places

More information: "Measurements on the reality of the wavefunction." Nature Physics (2015) DOI: 10.1038/nphys3233

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26 comments

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Doug_Huffman
1 / 5 (5) Feb 03, 2015
LOL Interpretations again. Will it be nooze every time a researcher discovers the many interpretations?
Doug_Huffman
1 / 5 (1) Feb 03, 2015
The preprint at arXiv
http://arxiv.org/...13v2.pdf
arom
1 / 5 (2) Feb 03, 2015
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?


Indeed when we know - physical mechanism of the WAVE function (not just a mathematical entity); then we could understand that whether the cat really alive or dead is just the weirdness in our head ….
http://www.vacuum...19〈=en
russell_russell
not rated yet Feb 03, 2015
Does a state contain all information or only all possible states?
richardwenzel987
not rated yet Feb 03, 2015
The cat can't tell us what it feels like, being both alive and dead. But set up an experiment with a human. Of course, use less drastic consequences, perhaps a hammer falling on a big toe. But if an observer in the box can tell us about the experience, hasn't the wave function already collapsed?
SoylentGrin
5 / 5 (1) Feb 03, 2015
But set up an experiment with a human. Of course, use less drastic consequences, perhaps a hammer falling on a big toe.


If 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_physorg
not rated yet Feb 03, 2015
The cat can't tell us what it feels like, being both alive and dead. But set up an experiment with a human.

Look 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.
IronhorseA
not rated yet Feb 03, 2015
The problem with interpreting the wave function is the fact that the atoms that make up the inside of the box (not to mention the air in the box) is just as valid an observer as we are, hence the cat is alive until it isn't (ie. the radioactive material decays and releases the poison).
Losik
Feb 03, 2015
This comment has been removed by a moderator.
rufusgwarren
not rated yet Feb 03, 2015
QM expresses a couple of things:

1. 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.
rufusgwarren
5 / 5 (1) Feb 03, 2015
Hence, if I have the correct tools I can tell you if the cat is alive or dead, asking me to do it any other way requires a psychic!
rufusgwarren
not rated yet Feb 03, 2015
I'm afraid this is my answer to Schroedinger.
rufusgwarren
not rated yet Feb 03, 2015
We know that everything that happens, quantum mechanically, will be observed with a wave function. trouble is, transforms of very rapidly changing charges will be interpreted with a spectrum, some of this spectrum is absorbed. Hence, bottom line, potential and kinetic "stuff" has rules. But what is actually going on, we need a little more analysis, we are just starting to get there.
rufusgwarren
not rated yet Feb 03, 2015
So we can solve schrodinger's cat when we can sense through walls, using his wavefunction to discriminate between wavelets that are evidence of death.
thingumbobesquire
not rated yet Feb 04, 2015
As I read this article, it simply dissolved into incoherence. Odd...
swordsman
not rated yet Feb 04, 2015
Physicists still don't understand a wave function?? Wow!
andy_barrette_5
not rated yet Feb 04, 2015
"either the wavefunction is completely real, or nothing is"... or the Copenhagen interpretation is incorrect! Why the De Broglie–Bohm interpretation is always left out of these conversations is a mystery to me.
Spaced out Engineer
not rated yet Feb 08, 2015
Ok so ontologically the waveform and reality may exist. I like it. Physicists are trying to help the fluffy philosophers argue a little less and get in the numbers.

My 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 Engineer
not rated yet Feb 08, 2015
http://journals.a...0.063630

I 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. ;)
Losik
Feb 08, 2015
This comment has been removed by a moderator.
Losik
Feb 08, 2015
This comment has been removed by a moderator.
Losik
Feb 08, 2015
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theon
1 / 5 (1) Feb 09, 2015
So they think they can measure the interpretation? But that is the domain of theoretical physics, that is: of modelling the physics. They better study dynamical models of measurements. What is to learn there: 1) Don't describe macroscopic objects by wave functions but by density matrices; 2) these describe an ensemble of systems; 3) the collapse is an effect on the description of the the ensemble by the density matrix. 4) You still need a connection to individual measurements, the so-called measurement problem. A new dynamical mechanism takes place that helps to do this, along with some weak postulates.
swordsman
not rated yet Feb 09, 2015
The cat is dead. Long live the cat!

Problem solved.
Losik
Feb 09, 2015
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Losik
Feb 09, 2015
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