Spontaneous wave function collapse can suppress acoustic Schrodinger cat states

October 28, 2014 by Lisa Zyga feature
Schrödinger's cat: a cat, a flask of poison, and a radioactive source are placed in a sealed box. If an internal monitor detects radioactivity (i.e. a single atom decaying), the flask is shattered, releasing the poison that kills the cat. The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive and dead. Yet, when one looks in the box, one sees the cat either alive or dead, not both alive and dead. This poses the question of when exactly quantum superposition ends and reality collapses into one possibility or the other. Credit: Wikipedia / CC BY-SA 3.0

(Phys.org) —Schrödinger's famous thought experiment in which a cat hidden in a box can be both dead and alive at the same time demonstrates the concept of superposition on the macroscopic scale. However, the existence of such "cat states" (or simply "Cats") would be problematic in reality, as cat states not only go against common sense, but also pose problems for understanding gravity and spacetime.

"Different people emphasize different concerns about Cats," Lajos Diósi, a physicist the Wigner Research Center for Physics in Budapest, Hungary, told Phys.org. "Some people emphasize different ones at different times. So, allow me to pick up two arguments. Penrose (in my words): A Cat implies of macroscopically different space-times, making physical time elusive. Myself: If we measure a Cat state a la von Neumann (why not?), then the collapse will macroscopically violate many conservation laws."

To address such problems, Diósi has expanded upon a model in which gravity-related spontaneous wave function collapses can suppress Schrödinger cat states, forcing them to take on only one value. Diósi's paper on suppressing cat states is published in a recent issue of the New Journal of Physics.

Several years ago, Diósi and Sir Roger Penrose each independently derived a model which can cause the spontaneous collapse of a cat state. This model came to be known as the DP model. According to the model, the measure of "catness" can be quantified as the difference between the two gravitational fields corresponding to the two states that make up a cat state. The greater the catness, the shorter the cat state's decay time.

Traditionally, the DP model is applied to single macroscopic degrees of freedom, such as the center of mass of a macroscopic object. In the new paper, Diósi has for the first time derived the DP model for the acoustic degree of freedom of a macroscopic object. Basically, he shows that macroscopic excitations, or sound waves, vibrating inside a macroscopic object such as a large rock will spontaneously decohere, meaning any acoustic cat states will collapse. The findings open up new perspectives on the concept of macroscopic superposition.

"Spontaneous models are usually thought to influence bodies under extreme isolated conditions [at very cold temperatures]," Diósi said. "I discussed the possibility that the DP might be significant in common phenomena. I don't mean a directly testable effect in acoustic waves, I mean a first step toward a theoretical search for parametric regimes where spontaneous collapse acts in the common matter of a common state."

Explore further: Physicists seek to quantify macroscopic quantum states

More information: Lajos Diósi. "Gravity-related spontaneous wave function collapse in bulk matter." New Journal of Physics. DOI: 10.1088/1367-2630/16/10/105006

Related Stories

Physicists seek to quantify macroscopic quantum states

June 29, 2011

(PhysOrg.com) -- "Scientists have been interested in generating and observing macroscopic quantum superpositions in order to test quantum mechanics at the macroscopic scale," physicist Hyunseok Jeong of Seoul National University ...

No qualms about quantum theory

November 26, 2013

A colloquium paper published in European Physical Journal D looks into the alleged issues associated with quantum theory. Berthold-Georg Englert from the National University of Singapore reviews a selection of the potential ...

Recommended for you

Theorists solve a long-standing fundamental problem

August 30, 2016

Trying to understand a system of atoms is like herding gnats - the individual atoms are never at rest and are constantly moving and interacting. When it comes to trying to model the properties and behavior of these kinds ...

Quest to find the 'missing physics' at play in landslides

August 30, 2016

During the 1990s, Charles S. Campbell, now a professor in the Department of Aerospace and Mechanical Engineering at the University of Southern California, began exploring why large landslides flow great distances with apparently ...

Invisibility cloak with photonic crystals

August 30, 2016

Almost as elusive as unicorns, finding practical materials for invisibility cloaking is challenging. Michigan Technological University researchers have new ideas how to solve that.

17 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Achille
5 / 5 (2) Oct 28, 2014
The Schrödinger's cat thing is just an analogy and in his description, the cat isn't actually a superposed wave function, the decaying state triggering the poisoneous gas is.

It is time to stop thinking we should find a way to make this analogy a reality.
Noumenon
1 / 5 (1) Oct 28, 2014
When Schrödinger proposed the thought experiment, to attempt to make the Copenhagen interpretation out to be an absurdity, he meant that the cat would be in a superposition as well. That was the whole point of it.
tritace
Oct 28, 2014
This comment has been removed by a moderator.
Ducklet
5 / 5 (3) Oct 28, 2014
The cat in a box isn't even a thought experiment - it's an illustration. It can't exist, because the cat continuously interacts (is measured by) the box, the air, it generates heat, its movement shifts the collective mass around, its breathing moves air, etc. It doesn't have a wave state separate from the box, which isn't separate from the person outside wondering if the cat is alive or not. To consider it some sort of paradox is silly; cats aren't superpositioned as long as they're alive and interact with the world. Cats aren't particles or condensates.
baudrunner
1 / 5 (3) Oct 28, 2014
The only valid point that the Schrodinger's cat paradox makes is that our perception of what is real and what constitutes reality does not always converge. That is analogous to the faster than light relativity theorem by which it is perceived that one cannot travel faster than light because one would have infinite mass and time would stand still, but the fact is that a person traveling at the speed of light exists in his own frame of reference, and he feels quite normal. It is the perception of the observer that yields those numbers.

There was a time when driving at 30 mph was considered reckless, and later that it was simply impossible to travel faster than the speed of sound.

I solidly maintain my status as a practical realist. And yes, this still allows me to believe in the ancient astronaut theory, because all practical analysis points to their being real. Mind-trippers turn the facts into mythical fantasy.
Noumenon
1 / 5 (2) Oct 28, 2014
The cat in a box isn't even a thought experiment - it's an illustration. It can't exist, because the cat continuously interacts (is measured by) the box, the air, it generates heat, its movement shifts the collective mass around, its breathing moves air, etc. It doesn't have a wave state separate from the box, which isn't separate from the person outside wondering if the cat is alive or not. To consider it some sort of paradox is silly; cats aren't superpositioned as long as they're alive and interact with the world. Cats aren't particles or condensates.


The point of a "thought experimen" is to remove all of that needless complexity, so as to focus on the point. The cat and poison apparatus is the quantum system.
arom
1 / 5 (2) Oct 28, 2014
Several years ago, Diósi and Sir Roger Penrose each independently derived a model which can cause the spontaneous collapse of a cat state. This model came to be known as the DP model….

Traditionally, the DP model is applied to single macroscopic degrees of freedom, such as the center of mass of a macroscopic object…. The findings open up new perspectives on the concept of macroscopic superposition.


It seems that people try to apply wave collapse phenomena (of micro object such as electron) to a macroscopic object such as cat - but unsuccessful; the problem is that the wave collapse arisen in microscopic realm in which we do not theoretically know how it works yet. Maybe understand the mechanism of electron wave could help ….
http://www.vacuum...19〈=en

qitana
not rated yet Oct 28, 2014
i'd like to post this link. It's relevant as it rejects the possibility of a collapse of the wave function. It rejects the Copenhagen interpretation on seemingly logical arguments. But I am no expert at all. I'd like to post it to have, perhaps, an opinion of an expert about it. Cheers

http://www.youtub...ecUuEqfc
Whydening Gyre
5 / 5 (3) Oct 28, 2014
The cat in a box isn't even a thought experiment - it's an illustration. It can't exist, because the cat continuously interacts (is measured by) the box, the air, it generates heat, its movement shifts the collective mass around, its breathing moves air, etc. It doesn't have a wave state separate from the box, which isn't separate from the person outside wondering if the cat is alive or not. To consider it some sort of paradox is silly; cats aren't superpositioned as long as they're alive and interact with the world. Cats aren't particles or condensates.


The point of a "thought experimen" is to remove all of that needless complexity, so as to focus on the point. The cat and poison apparatus is the quantum system.

No, it just adds complexity...
bee_farms_7
5 / 5 (3) Oct 29, 2014
it just means = something has to be *thought of* to happen

so entropy will kick-in in other words.
(because if the cat is going through time, then he is definitely one or the other = he is either definitely dead or definitely alive --- not both ---- either entropy is there or it isn't --- either time is there or it isn't ---- IF it's a real true alive kitten --- then he is either dead or alive -- not both.
theon
1 / 5 (1) Oct 29, 2014
Sadly, the Schrodinger cat paradox is mystified by the flawed assumption that macroscopic objects, such as cats, can be described by a wavefunction. Instead there should be a density matrix, describing our knowledge about an ensemble of cats.
Measurements will just reveal which ones are alive and which ones not; this eliminates all the hocus-pocus about living-dead cats.
And don't mention the wavefunction of the Universe, the one of my body does not even exist. There is, though, a Gedanken ensemble of myselfs (one real, the other ones in my dreams), just as in classical statistical physics one may imagine an ensemble with Gedanken copies of the macroscopic system one wishes to describe.
Tachyon8491
1 / 5 (1) Oct 29, 2014
I wonder why we are not told what the "DP" stands for. Surely that would have been informatively useful in the body of the article.
Whydening Gyre
5 / 5 (1) Oct 29, 2014
I wonder why we are not told what the "DP" stands for. Surely that would have been informatively useful in the body of the article.

You're not paying close enough attention to the content of the article -
Diosi/Penrose
You need to practice your reading comprehension skills...
Whydening Gyre
5 / 5 (1) Oct 29, 2014
it just means = something has to be *thought of* to happen

so entropy will kick-in in other words.
(because if the cat is going through time, then he is definitely one or the other = he is either definitely dead or definitely alive --- not both ---- either entropy is there or it isn't --- either time is there or it isn't ---- IF it's a real true alive kitten --- then he is either dead or alive -- not both.

Regardless of the cat's state, he is still THERE....
As are entropy and time...
Whydening Gyre
not rated yet Oct 29, 2014
Sadly, the Schrodinger cat paradox is mystified by the flawed assumption that macroscopic objects, such as cats, can be described by a wavefunction.

The cat's existence is the wave. It's state is the wave function.
I think the Schrodinger analogy is stupid.
Experience via experimentation (Science) has taught us that X time exposure to Y amount of radiation causes death.
Therefore, we know that if that happens, the cat will most assuredly be mostly dead or just plain dead. Just a matter of time...
antialias_physorg
5 / 5 (2) Oct 29, 2014
Sadly, the Schrodinger cat paradox is mystified by the flawed assumption that macroscopic objects, such as cats, can be described by a wavefunction

Since small objects can be described as a wavefunction: what scale limit did you have in mind where such a description is no longer correct?

Therefore, we know that if that happens

The point is that we don't know whether it happened (and neither does reality as it's still in a state of superposition of all possible outcomes)
Da Schneib
not rated yet Nov 01, 2014
Since small objects can be described as a wavefunction: what scale limit did you have in mind where such a description is no longer correct?
Worth noting that this has been confirmed in the laboratory, by using a laser to make molecules behave anti-entropically, proving the correct predictions of the Fluctuation Theorem. See also Bose-Einstein Condensates.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.