Schrodinger's Cat Experiment Proposed

September 24, 2009 by Sheeraz M. Hyder weblog
Schrodinger's cat

Schrodinger's cat. Image by Dhatfield, Wikimedia Commons.

(PhysOrg.com) -- One of the classical problems in quantum mechanics concerns a man and his feline companion. The man has placed his cat in an opaque tank and is slowing pumping it full of poison. Now until the man opens the tank and looks inside, he cannot be sure whether the cat is dead or alive. That is to say, the cat is both dead and alive at the same time. Impossible but such is the nature of the problem that faced this man. The man's name is Erwin Schrodinger and the problem is that of his Uncertainty Principle.

For nearly a century, his problem has remained a quixotic quest for physicists. has always held that matter can only exist at one state in one time. That is why particles are classified as moving with an up or down spin but nothing in between. In recent years that rule has been bent with the superposition of atoms and other nonliving things. Superposition is the term for an object that is not being observed that exists as both possibilities: up and down, dead and alive. This allows physicists to observe the matter in two different states at the same time. However, thus far it has only been done with non-living things. A life-form has never been superimposed. Now, one physicist says he may have an answer.

Oriol Romero-Isart is at the Institute for in Garching in Germany. Along with his team he is proposing a "Schrodinger's virus" experiment that would follow the same general principles of Schrodinger's Cat. Using an created by a laser, the virus would be trapped in a vacuum. Then, using another laser, the virus will be slowed down until it lies motionless in its lowest possible energy state.

Now that the virus is fixed, a single photon is used to put the virus into a superposition of two states, moving and non-moving. Up until the point is measured it is in both states. Only after a measurement is it found to be in one state and one alone. The team has suggested that the tobacco mosaic virus be used. The virus is rod-shaped and measures 50 nanometers wide and approximately 1 micrometer long. There is debate however, whether the virus can truly be classified as "alive." However the scientists are confident that the treatment could be extended to tiny micro-organisms such as tardigrades who can survive in vacuum for days, making them suitable for the "Schrodinger treatment."

However, physicists are doubtful about the experiment's results. Martin Plenio of Imperial College in London says that there is little reason that a virus would behave any differently than a similarly-sized inanimate object. However, there are possibilities in testing large objects such as viruses and molecules. This is because says that macroscopic objects can enter however, it has never happened. Through these studies, Plenio believes that we will finally be able to bridge the divide between the quantum world and our own macroscopic world.

More information:

• Towards Quantum Superposition of Living Organisms, arxiv.org/abs/0909.1469

• Schrödinger's cat on Wikipedia.

© 2009 PhysOrg.com

view popular send feedback to editors
3.5 /5 (46 votes)  

Filter


Move the slider to adjust rank threshold, so that you can hide some of the comments.


Display comments: newest first

bluehigh
Sep 24, 2009

Rank: 2.8 / 5 (9)
bad logic ...
That is to say, the cat is both dead and alive at the same time. - Wrong.

That is to say, the cat is EITHER dead OR alive at ANY GIVEN time.
OckhamsRazor
Sep 24, 2009

Rank: 3.3 / 5 (3)
bad logic ...
That is to say, the cat is both dead and alive at the same time. - Wrong.

That is to say, the cat is EITHER dead OR alive at ANY GIVEN time.


No that would depend on the interpretation, and there are several. That one would be the Copenhagen interpretation, I think. The dead and alive states exist at the same time and only when the box is opened does the wave function collapse into one of the two. It's flawed, granted, but I wouldn't say wrong. It's "interesting" :P
Silas_Wolfe
Sep 24, 2009

Rank: 2.5 / 5 (2)
Does no one remember that this was made as an idea, not as a test...?
Yes
Sep 24, 2009

Rank: 2.5 / 5 (2)
This experiment always took for granted that there is no subtle unknown communication system between all lifeforms that would collapse the state to either or.
bluehigh
Sep 24, 2009

Rank: 4 / 5 (4)
Granted that QM can be counter-intuitive but to defy logic and common sense does indeed bring science into disrepute. Thought experiment is being generous when assumptions are being made that have no basis in reality. Please show me any superposition on a macro scale. Show me just one cat that is both dead and alive. In our reality they do not exist. The wave function is always either that of a dead cat or that or a living cat.
To tell me that this cannot be seen because once I have a look the wave function collapses into one of the preferred states is (as davesmith suggests)pseuso-science or more accurately nonsense. Many respectable scientists (including) the venerable Einstein objected to the Copenhagen interpretation and chastised schrodingbat - was it not this context that brought forth the famous quote - God does not play dice with the universe.

And i too thought someone would be killing cats in boxes with poison - ahh practical science is much more fun!

Qubit
Sep 24, 2009

Rank: 3 / 5 (2)
One would never be able to prove that the virus was ever in a superposition of both states so it seems silly to undertake such an experiment. And as respectable as Einstein was the Copenhagen Interpretation is the most widely accepted interpretation.
rjpaton
Sep 25, 2009

Rank: 5 / 5 (7)
Uh, Guys.. Don't you think this article might be a hoax? Qubit is quite right - actually doing this experiment would be ridiculous. But more than that - has no one noticed the errors in the first paragraph? Firstly the description of the experiment is not correct, but also they attribute the Uncertainty Principle to Schrodinger! Heisenberg must be rotating at several hundred RPM in his grave!
NeuroPulse
Sep 25, 2009

Rank: 3.4 / 5 (5)
If you think this experiment is ridiculous or illogical, you do not know enough about quantum physics. People need to read some books on it. On the other hand, it is good that is your reaction to this because it means you get what they are saying. It is exactly as weird and counter intuitive as it seems. To quote Neils Bohr,"Anyone one is not shocked by quantum physics has not understood it." It has been around for about a century now, and most people are ignorant of it and how it radically changes out view of how the universe works. This experiment is serious. It is one in a progression of experiments using larger and larger objects to see how large of an object can exist in multiple states simultaneously. Photons were the first to be shown to exist in more than one place at the same time. Then electrons and protons and neutrons. Then alpha particles. Then atoms. Then increasingly larger molecules...
NeuroPulse
Sep 25, 2009

Rank: 5 / 5 (3)
...The larger the object the more difficult it is to keep it isolated and from interacting with something which causes the superposition to collapse into one state. It has been confirmed again and agian with very clever experiments that until a particle or object interacts with something on the macroscopic scale, it exists simultaneously in multiple states. Quantum computing exploits and depends on this. The question is what the heck is a macroscopic object? Where is the line, if there is one? There is much still to be understood.
rjpaton
Sep 25, 2009

Rank: 5 / 5 (3)
OK I guess I have to spell it out. Yes Neuropulse we get it. The Copenhagen interpretation of Quantum mechanics is "weird". The Schrodinger's Cat *thought* experiment was formutated to illustrate that weirdness & is a celebrated example - but it is only a thought experiment. The idea of actually performing the experiment is ludicrous. This guy Romero-Isart may or may not put his virus into a superposition of states but, as others have pointed out, there is no way to prove that the virus was ever in a superposition of both states! That's why its ridiculous to actually perform the experiment. Which brings me back to my original point - is somebody having a lend of us here? Can this article be for real? And why has no one else commented on the gross errors in the first paragraph - poor science journalism & pretty embarrassing for PhysOrg.com!!!
NeuroPulse
Sep 25, 2009

Rank: 5 / 5 (1)
Hello :-)

"The idea of actually performing the experiment is ludicrous. This guy Romero-Isart may or may not put his virus into a superposition of states but, as others have pointed out, there is no way to prove that the virus was ever in a superposition of both states!"

Do you agree smaller objects ranging from photons to molecules have been shown to exist in superposition? If so, where do you draw the line before reaching the size of a virus? If you disagree, then I should first point to specific experiments which demonstrate superposition. Or is it that you agree the virus would be in superposition, but this particular experiment does not show it? The physorg article does not explain that. See the original article "Towards Quantum Superposition of Living Organisms" as well "Towards quantum superpositions of a mirror"

"Can this article be for real?"

You mean the physorg article and not the article which it is discussing?
kasen
Sep 25, 2009

Rank: 5 / 5 (1)
I've read about this on another news site. The original article is for real, it has been proposed that virii be put in superposition by laser cooling. But I'm with rjpaton on this one, there are some serious problems with the above physorg article and not just in the opening paragraph.

This allows physicists to observe the matter in two different states at the same time.


That's just bogus. The very point of the experiment is that once an observation is made, there is only one state. Before that, it's not illogical, or counter-intuitive, to assume that you don't really know what's in the box, so the contents could vary wildly.

If you close your eyes, cover your ears and pretty much cut off all your sensory capacities, as far you're concerned, the world may not exist.

As far as marketing potential goes, Schrodinger really hit the jackpot with this one. The same is true for the potential for misunderstanding, unfortunately.
ShadowRam
Sep 25, 2009

Rank: 5 / 5 (1)
The uncertainty principle is simply a problem of metrology, but to say the cat is both, is retarded.

From a mathematical standpoint, yes it makes sense to say both exist to mathematically come to a statistical probability solution.

But too many even in the 'scientific' community is really taking this 'both exist' too literally.

Particles traveling ALL paths in space?
Infinite universes?

Drop the pipe, and step back into reality please.
SincerelyTwo
Sep 25, 2009

Rank: not rated yet
This thought experiment has been taking out of context way too far, to the point it is ridiculous.

It's not even meaningful on the microscope scale, it was designed to express certain problems of quantum mechanics in a more intuitive format.
tkjtkj
Sep 25, 2009

Rank: 5 / 5 (2)
"Copenhagen interpretation and chastised schrodingbat - was it not this context that brought forth the famous quote - God does not play dice with the universe."

But:
She does! 'statistical chance' is a foundation of QM, no?

and as i recall, wasn't Shrodinger's formulation made to mock QM, not to support it?

kasen
Sep 25, 2009

Rank: not rated yet
Heisenberg's uncertainty principle: http://en.wikiped...rinciple . Seriously, the article should be corrected or something.

As for Einstein's quote, it's just his opinion, not something scientifically demonstrated. QM talks about the statistical chance of measurement results, not of the actual events being measured.
Ant
Sep 25, 2009

Rank: 3 / 5 (2)
This idea is so daft I feel I must comment. As said previously the "dead and alive" logic is ilogical. At best the cat is alive or dead with the lack of communication being the problem. The cat cannot be alive and dead only the stupid would beleive this is the case. Now if the experiment put all those in the box that believe in the "and" case they would be able to communicate their status. This being that the response would be "im alive" until they were dead at which point they would stop communicating i.e the "or" case.
ben6993
Sep 26, 2009

Rank: 5 / 5 (2)
The 'alive or dead' aspect seems to be an unnecessary complication. Is the issue: how big can a molecule (or aggregation of molecules) be in order to be able to form an interference pattern in a double slit experiment?

Cats seem too big and delicate to use. We cannot project cats at large double slits and hope to look for an interference pattern where they hit the screen.

Though it would be a tempting idea to project camels at needles to test the old idea of not fitting a camel through the eye of a needle? They could only pass through the eye while in a QM superposition of states? Or perhaps not even then?
SmartK8
Sep 26, 2009

Rank: 5 / 5 (3)
So to sum it up for Mr/Mrs/Miss Hyder:

1) Erwin Schrödinger not Erwin Schrodinger.

2) Schrödinger was an opponent of the QM, not a proponent, thus this mockery experiment.

3) The uncertainty principle was formulated by Werner Heisenberg.

4) The fact that the cat is in a superposition is yet to be proven, because of its macroscopic scale thus (also the cat can be collapsing the state itself alone, which ofcourse doesn't mean it controls the outcome).

5) This experiment will try to - as NeuroPulse was trying to point out - determine if at least the viruses are also in this state or not => where is the border => what causes the collapse of the quantum state => it can be indeed very important experiment.

also:

6) to kasen: viruses not virii ;)
kasen
Sep 26, 2009

Rank: 5 / 5 (1)
I always thought viruses was used in computing context and virii in biology. Sounds more academic. Turns out it's the other way around. Thanks for the correction!

We cannot project cats at large double slits and hope to look for an interference pattern where they hit the screen.


Well, we could try. Actually, it'd be best to drop them on a double slit. The interference patterns should be made up of cats landing on their feet and cats landing on their backs.
PPihkala
Sep 26, 2009

Rank: 5 / 5 (1)
The man has placed his cat in an opaque tank and is slowing pumping it full of poison.

My knowledge of this is that radioactive decay (as in the picture) controls when the poison is released. Because that decay can not be predicted, the dead/alive state of the cat can also not be predicted.
ben6993
Sep 26, 2009

Rank: not rated yet
Is six atoms the current maximum group known/demonstrated (or whatever?) to be in a quantum state. See http://www.physor...606.html
Ant
Sep 26, 2009

Rank: 1 / 5 (1)
Sticking to the cat as the object considered in the original thought experiment what many of you seem to be saying is that superimposition exists through lack of knowledge of the objects status, in fact you are implying that this relates to any object where two states are possible but that the status is unknown. If this is correct then perhaps the word superimposition should be replaced with the word ignorance. This is certanly not the meaning when the word is related to quantum computing.
NeuroPulse
Sep 26, 2009

Rank: not rated yet
Is six atoms the current maximum group known/demonstrated (or whatever?) to be in a quantum state.


Carbon-60 molecules
http://physicswor...ews/2952

Tetraphenylporphyrin molecules
http://physicswor...ws/18187
Noumenon
Sep 27, 2009

Rank: 5 / 5 (25)
Yes tjktjk,
Schrodinger designed the 'cat' experiment to show how ludicrous the Bohr/Heisenberg model was. There are many other such 'thought expirements that are not cartoonish. The double-slit quantum eraser, Bohm-EPR, Mach-Zehnder interferometer, Elitzur-Vaidman bomb test, etc.
ben6993
Sep 27, 2009

Rank: not rated yet
If all electrons are created in complementary pairs (is that true?) then all the electrons in a cat will have their complementary partner electrons existing somewhere.

But if one partner electron annihilates with a third electron, where does that leave the unobserved singleton electron with respect to its quantum states? Presumably not entangled. Similarly, if one electron is observed then its unobserved partner's QM states will collapse.

I can't see anything wrong with the idea that bits of a cat exist in QM entangled states. But the idea that the whole cat is entangled is too statistically remote.

There is always a danger in using labels ('cat') that we treat the whole as one when it is made of many parts. There is a similar problem in refusing to believe that a bee can stop a 'train' in a head-on collision. A bee can stop the 'train' ... but not all of the train, of course, just a bit of it.
otto1923
Sep 27, 2009

Rank: not rated yet
@bluhi
bad logic ...
That is to say, the cat is both dead and alive at the same time. - Wrong.
Your 'logic' is what keeps you alive by making sense of the macroscopic world. It wouldn't help you much in the quantum one. Your ranks are dropping by the hour. Statistically you're becoming less... corporeal.

Why not start with cats for the experiment? Gas them and see what happens at the quantum level? Would the particle be both decayed and undecayed?
goatmin
Sep 27, 2009

Rank: 5 / 5 (1)
Um, maybe I'm missing something but aren't these two consecutive sentences mutually exclusive? "Superposition is the term for an object that is not being observed that exists as both possibilities: up and down, dead and alive. This allows physicists to observe the matter in two different states at the same time."
Reston
Sep 27, 2009

Rank: not rated yet
ripaton: "The Schrodinger's Cat *thought* experiment was formutated to illustrate that weirdness & is a celebrated example - but it is only a thought experiment. The idea of actually performing the experiment is ludicrous."

Here is Schroedinger's original paper on "Schroedinger's Cat".

http://www.tu-har...ml#sect5

I've linked the section specifically discussing the Cat. This "problem" did not vex Schroedinger. The whole point of his "cat paradox" is to ridicule the interpretation of his theory giving rise to it. He never accepted this interpretation of the theory. He never thought it a problem at all. He thought it much pseudo-scientific ado about nothing. His point is that we can actually perform the experiment, and we do actually perform similar experiments every day, but no one imagines half dead cats behind closed doors.
Reston
Sep 27, 2009

Rank: not rated yet
The experiment in the linked article has nothing to do with any cat being half alive and half dead. Quantum Mechanical systems can exist in a superposition of states, but so can classical systems. The complex shape of a vibrating guitar string is a superposition of simpler shapes, the sines and cosines of the Fourier expansion of the shape of the string.

And it's Heisenberg's Uncertainty Principle, not Schroedinger's.
ben6993
Sep 27, 2009

Rank: not rated yet
"Now that the virus is fixed, a single photon is used to put the virus into a superposition of two states.."
- -
Is the implication that the frozen virus is in only one possible QM state, or none, (or?). So the one photon associated with it carries the all the degrees of freedom for the virus/photon system?
In http://www.physor...562.html I asked whether, when the universe runs down, with entropy at its maximum, will there be no available QM states left in the universe. If this is the case, freezing the virus is in effect removing all the QM states from it? Just as it would if fully measuring/observing all of its elementary particles?

Continued ....
ben6993
Sep 27, 2009

Rank: not rated yet
Continued ......

Can the experiment about the virus/photon system give much more information than an experiment on the single photon, because the virus contributes nothing to the QM states? The article actually says that there are two states left so maybe the virus cannot be reduced all the way to a zero QM state. But I am not clear . But how can a QM experiment say much about a virus which is virtually QM-free? Or am I misreading it?
kasen
Sep 27, 2009

Rank: not rated yet
Not sure if I'm allowed this, but here it is: http://www.newsci...lab.html .

I think it explains what the experiment is about a bit better. If I understand correctly, the virus gets cooled to nearly 0 K, where it's in its lowest possible vibrational energy state. The photon can either be absorbed by it and push it up in its next level of energy, which corresponds to a new quantum state, or not. As such, the 'quantumness' of the photon infects the virus, so to speak, which is put in a superposition of energy states.

The experiment would prove that stuff bigger than molecules can be put in superposition. Not sure how they detect that, though. The virus's wavefunction probably gets correlated with that of the photon, which is known, so a series of experiments should show certain statistically significant results. Or something. Way out of my league.
ben6993
Sep 27, 2009

Rank: not rated yet
@kasen: Thank you for the link.

I have been wondering about the permanency of the quantum collapse of superimposed states. The cause of quantum collapse seems to be murky and I cannot believe it requires sentient observers. The inverse of quantum collapse is (say) quantum superposition formation. But can 'not observing' a system cause quantum superposition formation? I doubt it as it would imply collapse would be very fleeting.

Will the virus be 'infected' by the photon's QM superimposed state? Or will it still be a QM-inert virus with a photon associated with it? The question is: can we really make a quantum superimposition formation? We can collapse (completely for the virus) but can we really create?
Ober
Sep 27, 2009

Rank: not rated yet
you an show superposition by reacting an agent with the superposition. Then you get two different products from the reaction (if the superposition had two states).

Alternatively one state may not be reactive while the other is. If you had 100 virii in superposition and exposed them to a reagent, you might expect that the products would be split 50-50.

Just thinking out aloud.
ben6993
Sep 28, 2009

Rank: not rated yet
Thinking out loud, too...

The technology for this experiment is wonderful but the assumptions in it about QM are just assumptions, I think. The experiment cannot fail in QM terms, only fail in the technology.

A photon is to be fired at a translucent virus at zero deg Absolute. Somewhere in the virus, an electron in an atom will be lifted up by one notch in its energy level.

So this requires knowledge of what absolute zero temperature is with respect to QM. Does abs zero imply zero QM states? Does abs zero temperature imply all particles have an attribute (say position) known to within one Planck's length? Is that just the electrons in the shells, or the nucleii too? What is the commonsense interpretation of an electron (in a shell?) with position known so exactly? Is knowing an electon has in some way stopped moving less knowledge than knowing its position exactly? Are we sure there are no QM states left to observe in the frozen virus?
RayW
Sep 28, 2009

Rank: not rated yet
Isolate a recorder inside the box, capable of recording longer than the lifetime of a cat. Outside the box, superpositions exist. Review the record for a dead/alive cat when the box is opened, well after a cat's normal lifetime.

IMHO, superpositions and probabilities are tools for working with incomplete information, not a basis for multiple realities.
ben6993
Sep 28, 2009

Rank: not rated yet
"IMHO, superpositions and probabilities are tools for working with incomplete information, not a basis for multiple realities."
- - - - - - -

If they are not multiple realities, a lot of mainstream physicists are wasting their time trying to construct a quantum computer? As a quantum computer will need all those multuple realities?

"The complex shape of a vibrating guitar string is a superposition of simpler shapes, the sines and cosines of the Fourier expansion of the shape of the string"
- - - - -

Yes, but is this a series rather than a sequence? Ie an infinite sum rather than an infinite set of separate states? (Though I agree that classical systems ought to show QM states except for the statistical improbability of simultaneous preservation of a large collection of QM states.)
kasen
Sep 28, 2009

Rank: 5 / 5 (2)
If they are not multiple realities, a lot of mainstream physicists are wasting their time trying to construct a quantum computer?


Whether or not there are multiple realities is practically a matter of metaphysics. There are many interpretations of quantum theory, but the maths is the same for all of them and, most importantly, it works. That's all an engineer needs in order to make use of it in practical applications.

The first flying machines and steam engines weren't based on complete theories, either.
Rank 3.5 /5 (46 votes)
Tags

quantum mechanics, quantum physics, particle physics, max planck, schrodinger s cat, superposition, electromagnetic field
Related Stories
more news
Relevant PhysicsForums posts
  • Strength of induced magnetic field inside an inductor
    created2 hours ago
  • Physical laws .... are they material?!!
    created2 hours ago
  • increasing time of daylight
    created3 hours ago
  • Light & Sight
    created3 hours ago
  • Wind Turbine Power
    created6 hours ago
  • Steam Table issues
    created8 hours ago
  • More from Physics Forums - General Physics

More news stories

Putting the squeeze on planets outside our solar system

(PhysOrg.com) -- Using high-powered lasers, scientists at Lawrence Livermore National Laboratory and collaborators discovered that molten magnesium silicate undergoes a phase change in the liquid state, abruptly ...

Physics / Condensed Matter

created 2 hours ago | popularity 5 / 5 (1) | comments 0 | with audio podcast

Hovering not hard if you're top-heavy, researchers find

Top-heavy structures are more likely to maintain their balance while hovering in the air than are those that bear a lower center of gravity, researchers at New York University's Courant Institute of Mathematical Sciences ...

Physics / General Physics

created 3 hours ago | popularity 5 / 5 (1) | comments 1 | with audio podcast

SLAC, Stanford team focuses on high-energy electrons to treat cancer

Accelerator physicists at SLAC and cancer specialists from Stanford are working on a new technology that could dramatically reduce the time needed for cancer radiation treatments. The team ran an initial experiment ...

Physics / General Physics

created 6 hours ago | popularity 5 / 5 (1) | comments 0

Measurements from high-energy collisions lead to better understanding of why meson particles disappear

For several years, physicists at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), USA, have studied an unusual state of matter called the quark–gluon plasma, which they ...

Physics / General Physics

created 7 hours ago | popularity 5 / 5 (1) | comments 0

Quantum physicist explains $100K offer for proof scaled-up quantum computing is impossible

(PhysOrg.com) -- MIT researcher Scott Aaronson has certainly riled the physics community with his offer this past Friday, of $100,000 to anyone who can prove that scaled-up quantum computing is impossible. ...

Physics / Quantum Physics

created Feb 08, 2012 | popularity 4.1 / 5 (11) | comments 32 | with audio podcast weblog


Complex wiring of the nervous system may rely on a just a handful of genes and proteins

Researchers at the Salk Institute have discovered a startling feature of early brain development that helps to explain how complex neuron wiring patterns are programmed using just a handful of critical genes. ...

CIA website offline, Anonymous takes credit

The website of the Central Intelligence Agency was unresponsive on Friday after the hacker group Anonymous claimed to have knocked it offline.

Q&A: Obama and the birth control controversy

(AP) -- What birth control debate? A half-century after the introduction of the pill, acceptance of birth control by American women is virtually universal.

The power of estrogen -- male snakes attract other males

A new study has shown that boosting the estrogen levels of male garter snakes causes them to secrete the same pheromones that females use to attract suitors, and turned the males into just about the sexiest ...

New error-correcting codes guarantee the fastest possible rate of data transmission

Error-correcting codes are one of the triumphs of the digital age. They’re a way of encoding information so that it can be transmitted across a communication channel — such as an optical fiber o ...

Human cognitive performance suffers following natural disasters, researchers find

Not surprisingly, victims of a natural disaster can experience stress and anxiety, but a new study indicates that it might also cause them to make more errors - some serious - in their daily lives. In their upcoming Human Fa ...