WANTED: CAT: Dead or Alive

I think that if you take a picture of a sleeping cat, you can't tell it's not a dead cat. But it doesn't have anything to do with quantum mechanics.

Probably nobody really understands quantum mechanics. The theory and mathematics behind it work perfectly, but nobody knows why. It's as if we all own automobiles and know how to put gas in and what the controls do and how to drive them, but we have no idea of what's inside or how they work. It's not very satisfying.

We don't have a model with what happens at the quantum level. For example, light acts like a particle in that it is quantized, a single photon can eject a single electron from an atom. But a single photon can act like a wave, it can travel two paths and when recombined can exhibit interference. And "particles" like electrons, atoms, molecules, and presumably any other piece of matter behave in the same particle/wave fashion.

Our models try to come up with an analogy to something we can see, billiard balls or water waves. Whatever is happening in the quantum world, it apparently isn't anything that has a macro world analogy.

Erwin Schrodinger came up with the thought experiment of a cat locked in a box with a bottle of poison which would be released if a radioactive atom decayed. He did this to make the point that if the radioactive atom was in an undetermined state until observed (by opening the box) as required by the Copenhagen interpretation then so was the cat. It was ridiculous that the cat was both dead and alive, and so the Copenhagen interpretation could not be right.

"Schrödinger's cat: a cat, a flask of poison, and a radioactive source are placed in a sealed box. If an internal monitor (e.g. Geiger counter) detects radioactivity (i.e. a single atom decaying), the flask is shattered, releasing the poison, which 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."

https://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat

Modern thinking is that "observed" doesn't imply a human opening the box. It makes no sense that physics operated differently before humans were around. "Observed" now is referred to as "decoherence". Decoherence is when a quantum system interacts with the external world. As soon as the subatomic particle from the radioactive atom makes a change to the external world, this is a non-reversible event and decoherence has taken place, "collapse of the wavefunction".

There is no cat that is "neither dead nor alive".

https://en.wikipedia.org/wiki/Quantum_decoherence

The moment you observe or measure in any way, the cat, is kaput....

The picture just presents an image of the cat in the past. The picture might be ambiguous, therefore knowledge of the cat's condition can only remain as unknown in this scenario. If the image unambiguously shows a dead cat then one now knows they have a dead cat. If instead the image unambiguously shows a living cat then one still does not know the present status of the kitty.

I am assuming that the photo is taken when the cat has been in the box with the poison mechanism and all. As I understand it, according to the Copenhagen interpretation, until an "observer" sees the photograph, the cat is still both dead and alive and the photo itself is both a photo of the live cat and of the dead cat.

The question that I have never heard asked, let alone answered, is what happens if the cat is also an "observer" (or if the subject in the box is not a cat but rather a human). Then it does not depend on a human looking inside because it has already been observed. But if the cat dies, then can it still be an observer? If not, then it can only be in a mixed eigenstate if it is not in a mixed eigenstate because it is dead and no longer an observer.

Is there anyone at all who is following this and can correct my logic?

To me the big problem is defining an observer. I used to think that all it took was for an atom to be "observed" by another atom that it interacts with, and then its eigenstate would collapse. But then I read that you can launch peptides (small proteins with perhaps dozens or hundreds of atoms) through a grid at a target and they cause interference patterns on the target, which means that all the interactions happening within the peptide are not enough to cause it to collapse. And I also read that photosynthesis has actually evolved to become more efficient by taking account of the mixed eigenstate, which means that a photon does not lose its mixed nature when it interacts with chlorophyll.

So I think there is much we don't understand about quantum physics, but you all knew that.

A dead observer is not very observant. So I think there is some flaw in that logic.

Here is the (possibly flawed) logic in question:

"But if the cat dies, then can it still be an observer? If not, then it can only be in a mixed eigenstate if it is not in a mixed eigenstate because it is dead and no longer an observer."

This is the paradox I wonder about. But just because it causes a paradox, does that mean it is not true? Or does it mean that the cat cannot die? Or does it meant that if the cat dies it immediately returns to life, or at least "half-life."

If the cat dies, she dies! Its nine lives over in a split second.

I cannot see the paradox.

It is not that this world needs an observer to exist. But for any observer if he exists a world has to be there. The world will not exist anymore for the observer if the observer dies, but as per my first comment in this paragraph, the world will still exist.

I have been observing this for all of my life and I have not seen any evidence to the contrary. Does that mean I am still alive?

I think you're right. I was thinking that the paradox comes about if you assume that Schrodinger's Cat actually is both alive and dead at the same time, and also that the cat is an observer that can cause the mixed state to collapse into either alive or dead.

So if the cat observes the poison being released, it dies, but then it stops observing the system, and it resumes being a mixed state. If the cat does not observe any poison being released, then the cat is alive. It seems like there is only one stable output, which is that the cat is alive, no matter whether the poison is released or not.

But now I think that if the poison is released, the cat dies, stops observing the system, but the system does not return to being a mixed state. It is too late. The cat is dead. Long live the cat!

The sentence below is true.

The sentence above is false.

I think I follow. But I don't really know what "eigenstate" means. Vague/undefined state? But, I think the real key here is knowing what the prerequisites are for an observation to occur. If an observer has nothing to observe, does an observation actually take place? Can you really "observe" nothing? The flip side of that is, if something cannot leave any trace of its existence, can it really be observed? If a true quanta actually exists, then the only way for it to leave behind any evidence of its existence, is for it to no longer exist. Because any trace left behind, requires that that quanta "give up" something that CAN be detected.

But by definition, a quanta is an "all-or-nothing" thing. Therefore, a quanta can only exist as "non-observable", or cease to exist when "observed". Consider this: Normally, we need light to see anything. We can not see in the dark. So, how can we "see" light/photons? If light was "observable" then light itself would be opaque and we couldn't see anything else. The best we can do, is detect the effects of photons without actually observing them. And when any effects ARE detected, that photon(s) ceases to maintain the whole value of what a quanta consists of, thereby ceasing to exist.

Also, When we try to "shed light" on such small particles, that very light becomes relatively huge to the thing being observed. And we become "blinded by the light", while the thing trying to be observed becomes lost in that observation. In other words, normally, light is massless and bounces off normal objects without any noticeable interference. But when the thing being observed is equal-to/smaller-than a photon, there is no way that that observation/detection can remain unaffected. Both the observation and the being observed affect each other. But, if both the observing and the being observed consists of all-quanta "things", then by definition, only one can survive, while the other ceases to exist. No quanta can leave behind only a part of itself (it's all or nothing). Which will be "the last man standing"? In a case like this, you don't know if "curiosity killed the cat", or "curiosity destroyed the observed". In other words, in the quanta world, there might be no such thing as non-destructive testing/observing.

Schrodinger came up with the thought experiment of the cat and box to illustrate the illogic of the Copenhagen interpretation of quantum theory, that it implied the absurdity that a cat could be both dead and alive until a human observed it. The Copenhagen interpretation is that it requires a "consciousness" to observe an event before it becomes real.

My question is what happened millions (or billions) of years ago when there were no "observers". Events happened back then without our help. There are a lot of craters on the moon that happened long before "observers" were around. Or did they appear the first time someone looked at the moon?

We can see quantum paradoxes without any observer being involved. A good example is that light can be observed as a particle or as a wave, depending on how the experiment is carried out. This selection can be carried out by a computer, no conscious observer involved.

An interferometer can be set up to determine whether light is a photon which follows one path or a wave which follows two paths. This interferometer consists of a beam splitter, two mirrors, and a second beam splitter which can be electronically removed, very quickly, even after the photon is inside the interferometer.

If the last beamsplitter is missing (top) the photon is detected either with one detector or the other, never both. This implies that it either took the red path or the blue path. If the beamsplitter is in place, the interference pattern appears, indicating that the photon took both paths and interfered with itself.

https://www.kisspng.com/png-wheeler-s-delayed-choice-experiment-delayed-choice-2638483/

What I disliked of the Copenhagen interpretation of quantum mechanics is they seemed to have forgotten that this is a false mathematical probability paradox. Prior to the observation of the state or an effect caused by the state the probability is the only thing that is known is the probabilities of the state not the actual state itself.

Regarding what happened billions of years ago, John Wheeler came up with what he called the Participatory Anthropic Principle, which states that the universe evolved in all possible states, or in other words, no actual state, but that when one of those states became capable of observation, then all the quantum superpositions of all the atoms in the universe collapsed into the one state that contained an observer. Perhaps humans.

In other words, intelligence is necessary for the existence of the universe.

I really enjoy that theory, though I have no idea whether it is true. I also enjoy the idea that no observer can be a part of the same system that contains it. In other words, no entity made of atoms or photons can cause the collapse of the wave equations of any other atoms or photons in the same universe. No ordinary human body (or cat's body) can be the kind of observer that causes such collapse. It requires the observation of someone outside the system, like a spirit or soul inhabiting a human body. Or perhaps God.

Here's a novel you might like. I'm rereading it now.

https://www.amazon.com/Quarantine-Novel-Greg-Egan/dp/1597805386

If the cat is dead when put in, could it spontaneously come back to life?

In a thought experiment, it can do anything you like.

Maybe. But hopefully, there will be some redeeming quality to it, even if it's just amusement.

OK, so walking undead cats are not off the table.

Interesting.

In my opinion,the state of the cat is fixed before the door is opened.

The uncertainty of it's state exists only in the mind of the observer prior to the observation.

We simply cannot know what we don't know,or we would know everything.

The uncertainty is a mental aspect of the experiment, not an actual one.

In order to be a mental construct,there must be a mind capable of pondering the possible states of the cat.

Consider the possibility that you do not exist,if you can.

If you do not exist,for all intents and purposes,nothing exists.

Can you prove that anything exists outside of your sensory inputs?

Is the universe unique for each observer?

Do we each see the universe slightly differently,and is the universe truly relative to each observer?

Will the universe exist after you die?Can you prove it?

The big obstacle in developing a quantum computer is maintaining the superposition state long enough for a computation to take place. It requires extreme measures of isolation from the environment including cooling to close to absolute zero. In a relatively short time, the isolation is violated and the superposition is destroyed, the wavefunction collapses into a single eigenstate, a process called decoherence.

"Decoherence, Quantum Computing’s Greatest Challenge

Superposition for subatomic particles is like balancing a coin, any small movement, vibration or even sound can affect the coin from being in a neutral state to collapsing on either heads or tails (0 or 1)."

"The decoherence theory is reverting a quantum system back to classical through interactions with the environment which decay and eliminate quantum behaviour of particles.

Due to decoherence qubits are extremely fragile and their ability to stay in superposition and or entangle is severely jeopardized. Radiation, light, sound, vibrations, heat, magnetic fields or even the act of measuring a qubit are all examples of decoherence."

https://hackernoon.com/decoherence-quantum-computers-greatest-obstacle-67c74ae962b6

No way is the cat going to be in a superposition state. In practice, the environment destroys the superposition state, the superposition state does not expand into the environment (i.e. the cat).

Ok,consider this scenario:

Two observers:one viewing the box directly,the other viewing it on a monitor fed by a very long fiber optic cable,a cable 1 light year long.

When does the decoherence occur?

When the first observer sees it or the remote viewer?

What if there is only the remote viewer?

As for the photon double slit experiment,at light speed,time stands still for the photon.

A single electron could take both paths and we could not tell the difference because we are locked into local time.

Judging from the difficulty that people trying to build quantum computers in maintaining a superposition state, I believe that as soon as the Geiger counter records the radioactive decay, decoherence has occurred.

As soon as there is any indication in the real world, the superposition state is gone, decoherence has occurred.

It's better to analyze a real experiment than a thought experiment, IMHO.

Consider the case where a single photon goes through the interferometer in both directions, which it can do because it is in a superposition state. (Don't ask me how, but apparently, it can!) It is in a superposition state until it strikes a photographic plate where it ionizes a single silver atom. This experiment is repeated thousands of times, and each time a single photon travels both directions and strikes a single silver atom.

For one photon, it is not obvious anything unusual is going on, but after there are thousands of points on the screen, it is seen that they form a banded interference pattern. The superposition state is invisible, and its existence is only detected by the evidence it has left behind after the decoherence as each photon made its position known by an ionized silver atom.

Decoherence occurs when the photon hits the photographic plate. It makes no difference if any human, cat, or any other creature observes it.

In the double slit experiment,is the slit and target in a vacuum chamber,with no interference from atmospheric properties?Is it magnetically shielded and shielded from all other outside influences?

Does the spacing and size of the slits and thickness of the plate with the slits have any effect on the outcome?

Young's double slit experiment is a demonstration of wave and interference properties.

The experiment can be seen in a ripple tank with slower moving waves.

The spacing between slits and the wave length should be similar or the peak nodes and anti-nodes are less apparent. Also a wave with very little wave length dispersion is preferred to see this effect.

I understand waves. But, these waves are traveling thru a volume of countless molecules with mass that can transfer energy from one to another. I still don't see how a single photon can do this by itself.

That is one of the paradoxes of quantum mechanics and the particle/wave duality of light.

What really baffles me is this has been repeatedly demonstrated with individual electrons flying one at a time through a very tiny double slit. Each electron strikes a positional detector (phosphorous screen) and single electrons clearly reach the detector. However, if one takes a summation of many discrete, individual electron detections one still finds the exact same interference pattern reaching the detector. Now how a well known individual particle interferes with itself, I cannot grasp. But it does.

It seems to me, that the only explanation could be that those "individual" electrons are actually traveling thru some unknown field that is creating those waves. However, if those electrons are a quanta entity, then once those those electrons hit that unknown field, then those electrons must give up their ENTIRE quanta of energy to that field, and cease to exist. From then on, it's the ENERGY from the photons (and not the photons themselves) that create the waves. There just has to be some kind of "change of form" from one energy to another. After all, "energy is neither created nor destroyed, only changes in form.".

'... the only explanation could be that those "individual" electrons are actually traveling thru some unknown field that is creating those waves. ...'

.

Yet, when only one slit is provided through which to pass, the interference pattern does not show up. The unknown field you propose would need to be a special field that is negated by a single slit (or alternately that requires multiple slits).

I've never seen a single any thing interfere with itself (except a snake eating its own tail).

"The unknown field you propose would need to be a special field that is NEGATED by a single slit (or alternately that requires multiple slits)" ? How do you figure?

How do I figure? Quite well, though I probably have some bias in this evaluation.

The photons or electtons will show an interference pattern if there are two slits (or more) but not if there is onlu one slit.

The fact that you haven't experienced similar in usual macroscopical scenatios is a testament to the unintuitive nature of things on a very small scale.

" but not if there is only one slit.". Ok, no argument here. I hope I didn't say otherwise.

A little bit of clarification on this often repeated experiment is needed to show how weird is the final result. The path of the electrons is from A through slits S1 and/or S2 and then impacting somewhere onto the detector B. The transit time from A to B is arbitrarily set for this clarification at 1 ms. One and only one electron is sent every 10 ms and one and only one electron is detected on the detector array every 10 ms. After many hours of accumulating data, an interference pattern still emerges from the accumulated data.

Hitachi posts a nice document on this experiment.

If you are using electrons, then yes, you need a vacuum. You would want to shield from strong electric or magnetic fields. By de Broglie's formula, the wavelength of a moving electron is inversely proportional to its momentum. (λ=h/p, where λ is wavelength, p is momentum, and h is Plank's constant.) To get a good interference pattern, all the electrons should have about the same momentum so that they have the same wavelength.

Note: Since a macroscopic object like a baseball has considerably more momentum than an electron, its wavelength=h/p is extremely short, so baseballs do not exhibit any detectable wavelike behavior.

Let the distance from the slits to a point on the screen be d1 and d2. If the difference between d1 and d2 is an integral number of electron wavelengths, there will be a high probability that the electron will arrive there. If this difference is an integral number + 1/2, there will be zero probability that the electron will land there. This causes the interference pattern.

If you're using photons, you don't need a vacuum chamber or magnetic isolation. Photons don't interact that much with air. Again, to get a good interference pattern, the light should have the same wavelength, e.g. laser light.

https://en.wikipedia.org/wiki/Double-slit_experiment

If you have a laser pointer, you can easily see the interference pattern by holding a hair in the beam. This produces a pattern much like the double slit experiment.

In the double slit experiment, the closer the slits, the wider the pattern. The thinner the slits, the sharper (but dimmer) the pattern. The thickness of the plate (within reason) does not have much effect, as far as I know.

Here is a real-world model that sort of reproduces the effect of electron interference. You flip a coin into the air. The coin is in a superposition state when it is spinning in the air, and when it lands (interacts with the environment, i.e. floor) it decoheres into an eigenstate of either heads or tails. The distance the coin travels through the air and the rate of spin (f = Energy/h) determine the eigenstate (heads or tails).

If you had a machine that could accurately flip a coin, you could create a heads/tails interference pattern by varying the distance the coins travel through the air, maybe by varying the height from which the coin was launched.

This is one reason why I don't like quantum physics. There always seems to be the necessity to say things like, "As soon as there is any indication in the real world.". Well, if it's so hard to relate this to the "real world", then maybe it can't really be real itself.

But then again, progress comes from "analyzing thought experiments". The key is to recognize the difference between facts and potential facts. Or as Ted Kennedy said about his brother Robert, "Most people see things as they are and ask 'Why?'. He saw things as they could be and asked 'Why not?'".

In quantum physics, when you talk about particles and photons and leave cats aside, it seems to be clear that the uncertainty of the state exists as an actual aspect of the situation, not just in the mind of the observer. This is the interpretation of the double slit experiments with electrons.

https://en.wikipedia.org/wiki/Double-slit_experiment

I assume you are familiar with that experiment, but I will summarize here for anyone unfamiliar with it. If you shoot electrons through two very tiny slits very close to each other, and then use a phosphorescent screen to find out where they went, the electrons form an interference pattern on the screen, just like water or sound waves, even if there is only one electron passing through the slit at one time. The electrons interfere with themselves, acting like waves. But if you put a detector at one of the two slits, the interference pattern disappears and the electrons act like bullets, passing through only one or the other slit and making only two lines on the screen.

The experiment demonstrates the observer effect, which means that a particle does not actually occupy any given position until you observe it, and then its probability wave collapses and it is found only in one position. One big debate is what constitutes an observation and what constitutes an observer.

When you add a cat, all bets are off, because there is a high probability of them napping.

I would prefer the cat be dead. I don't like cats.

Now, now. Cats are not-people too.

Hmm... Is there a subliminal message here? I'm a people; Do you hold that against me? I can't help it if I was born on the wrong side of the tracks.

Why did the chicken cross the tracks? Because it didn't want to be a chicken any more.

Then you deserve all the mice not caught in a prior discussion!

Correct! Insufficient information.

Quantum computer solves problem without actually running!

Check out this link:

https://www.sciencedaily.com/releases/2006/02/060223084147.htm

"Curious-er and curious-er" said Alice.

"Next stop,the Twilight Zone"--(from the tv series of days gone by.)

Your experiment has three possible states for the cat (given eyes closed) and they would seem to be

• Cat alive, eyes closed.
• Cat recently dead, eyes closed.
• Cat Prolonged dead, decomposing/decomposed.

There will be a progressive increase in probability of the third state as the experiment continues until not only is the state of the cat certain, but also the ability to determine that condition would become certain.

Now, what if the cat was an expectant female. Would the offspring also be "Schrodinger's cats" with multiple possible states with some alive and others not?

Heisenberg and Schrödinger get pulled over for speeding.

Heisenberg and Schrödinger get pulled over for speeding.

The cop asks Heisenberg "Do you know how fast you were going?"

Heisenberg replies, "No, but we know exactly where we are!"

The officer looks at him confused and says "you were going 108 miles per hour!"

Heisenberg throws his arms up and cries, "Great! Now we're lost!"

The officer looks over the car and asks Schrödinger if the two men have anything in the trunk.

"A cat," Schrödinger replies.

The cop opens the trunk and yells "Hey! This cat is dead."

Schrödinger angrily replies, "Well he is now."

https://www.reddit.com/r/Jokes/comments/1k7rp6/heisenberg_and_schr%C3%B6dinger_get_pulled_over_for/