In the experiment of Einstein, Podolsky and Rosen (APR experiment), it is found that the properties of one particle are determined by the results of the measurement of the other particle. means that observing one side of the experiment causes the quantum state to collapse to a specified value.
An orthodox quantum description of a system is bound by three elements: a quantum state (a vector in Hilbert space) is associated with the system. The Hamiltonian of the system determines how this state will evolve over time as long as no measurement is performed on the system. Finally, when a measurement or observation of the system is performed, the quantum state changes discontinuously and this reflects the result of the measurement, which is called wave collapse.
When measurements are made on two separate and distant particles, but the particles are quantum correlated, i.e. in a state of quantum entanglement, as in the experiment of Einstein, Podolsky and Rosen (APR experiment), one finds that the properties of one particle are determined by the results of the measurement on the other particle. means that observing one side of the experiment causes the quantum state to collapse to a specified value. What value is set to? According to the orthodox interpretation of quantum mechanics this is beyond our control. The collapse of the wave function is an immediate process and independent of the spatial separation between the two particles.
Einstein, Podolsky and Rosen proposed the EPR experiment in 1935. From the predictions of quantum mechanics and the uncertainty principle, there are certain groups of variables, one of which is known with certainty and the other is completely unknown. In the mathematical language of quantum theory, it is said that if the operators for two observable variables are not commutative, only one of the two variables can be known exactly at a given moment. If we take the position and start as an example. The uncertainty principle tells us that if we know the exact momentum of the system, say of a free particle, its position is completely unknown. So if the momentum of a particle is known with a probability of 1, we cannot know with a probability of 1 the position of that particle.
As a result of Heisenberg's uncertainty principle, incompatible quantities cannot be determined with certainty. It seems that this violates the sufficient condition for the realism of a physical quantity, according to which a physical quantity can be predicted with certainty without disturbing the system - (or the measurable characteristics of the physical system exist and are well defined separately from any external influence and observations). Therefore, if according to the uncertainty principle a quantity cannot be predicted with absolute certainty, quantum mechanics is incomplete. If the position and momentum of a particle cannot be known with certainty at the same time, Einstein thought that quantum mechanics is incomplete, that something is missing, something realistic (hidden variables) that would allow us to know them with certainty. But one can think that quantum mechanics is completely complete and that nothing is missing in its explanation. In such a case the result of the uncertainty principle simply tells us that, in principle, incompatible values cannot be determined with certainty at the same time.
APR decided to refute this claim. With the help of an experiment, Albert Einstein sought to show that complementary quantities (especially position and momentum) can have realistic values, elements of reality, at the same time; Then the obvious conclusion is that there is no explanation in quantum mechanics that would contain them. Therefore, the description provided by the wave function of the system will not be complete and it cannot be concluded that quantum mechanics is complete.
Aper proposed the following experiment in 1935: Suppose we have two systems A and B (which could be two free particles), whose wave functions are unknown. Then they interact for a short time and the wave function resulting from this interaction can be determined using the Schrödinger equation (the year is 1935...). Suppose now the systems are moving far apart, so far apart, that they can no longer interact with each other in any way. According to the theory of special relativity they are separated in such a way that no light signal can pass from one system to the other. Measurements made far apart cannot affect each other. This condition means that the probability of a measurement on A is a function of the variables of A only. This condition is the locality condition. But the values of system B can only be deduced from the collapse of the wave function. At the time of measurement the two systems are no longer interacting. Therefore, it is logical to assume, Einstein concludes, that if the two particles A and B were previously interacting and now they are separated, the results of the measurements on A should not affect B in any way. This condition means that the probabilities for the measurements performed on A and B can be separated (the probabilities for the measurements of A and B are two separate and independent functions). This is the separation condition (spheribility). That is, while measurements are performed on system A there is a reality that belongs to system B only. Thus system B maintains its separate identity even though it is related to A.
But if we proceed from the assumption that quantum mechanics is a complete theory (the orthodox interpretation of quantum mechanics obtained as a result of the Copenhagen compromise), the measurement on A telepathically changes the state of B (violation of the principle of locality and spheribility), because the change occurs instantly while transferring information at an infinite speed and this violates the principle of constancy of the speed of light in the special theory of relativity; and therefore violates the simultaneity relation.
Einstein, of course, immediately called out and said that in view of this blatant contradiction, if even though A and B are spatially separated - non-locality - they are both considered one system, i.e. a wave function in superposition and are not considered two separate real parts, then a separate existence must be attributed to each of the two parts of the system . We must look at the two spatially separated systems A and B as having separate realistic states, which are independent of the act of measurement. And so Einstein concludes that realistic values must be assigned for the momentum and position of system B.
In 1950, David Bohm reformulated the original APR experiment in the form of measuring half-spin particles. By analogy with Bohm's thought experiment, since it is easier to measure the polarization of photons than the direction of half-spin particles, a polarization filter can be used instead of a Stern-Gerlach device. We will examine two particles, which as a result of some interaction or some creation process, each of them can get one of two possible quantum states. Let's say the particles are photons and the two possible states are vertical and horizontal polarization. The two photons always emerge from the interaction in opposite states of linear polarization: one vertical and the other horizontal, but not both horizontal or both vertical. We have no practical way of knowing which photon emerges in which state.
The combined two-particle quantum state is a linear combination of the product of the states of the two photons. As a result the photons have lost their independence and are in quantum entanglement. In 1964, John Bell published a thought experiment - which is a version of the EPR experiment, the (EPRB) EPR-BELL experiment - designed to distinguish between quantum mechanics and local hidden variable theories. In Bell's version of the APR experiment, quantum mechanics and local hidden variable theories statistically predicted different experimental results.
The version of Bell's experiment, an experiment (EPRB), was carried out in the laboratory by Alan Espa and the predictions of quantum mechanics were confirmed; And so Einstein's idea according to which a separate existence must be attributed to each of the two particles in the quantum entanglement because of the contradiction with special relativity fell flat. Bell demonstrated theoretically that if the values in the correlation were due to local causes, as Einstein believed, they would provide a series of inequalities, which in many days were called "Bell's inequalities" after him. But according to the interpretation of orthodox quantum theory and the experiments performed by Aspa and the later experiments, Bell's inequalities are violated by an instantaneous and non-local collapse of the wave function for the two photons; Therefore, it is not possible to explain the correlation between the particles in the APR experiment on the basis of local causality.
http://arxiv.org/pdf/0707.0401v3.pdf
If you examine the APR experiment in the reference system of the laboratory and look at Minkowski's space-time diagram, you find that the measurement events of the quantum particles in the APR experiment have a spatial-like separation. Therefore, as Einstein first noticed in 1935, if one wants to provide an explanation for an experiment based on local effects of one particle on another, the explanation should be based on effects that move at a speed higher than that of light, in fact at an infinite speed; It can also be said this way: the action at a distance should be returned to physics, which acts immediately, acts on a particle that is at a huge distance from our measuring device. A non-local connection between two distant particles represents many difficulties in interpretations in quantum mechanics and is the focus of tensions between quantum theory and special relativity - and because of these tensions, Einstein wrote about ten years later to his friend Max Born in 1947 that this is "action at a distance of ghosts".
But most of the time researchers still thought that there must be a strange communication between the particles in quantum entanglement and they asked themselves: can we take advantage of the strange communication that exists between the distant entangled photons to send messages quickly on Orit?
We will examine a thought experiment in which there is a telephonic communication system that operates on the principle of quantum entanglement. The system has a transmitter, a receiver and a wire that connects them and consists of two correlated photons, which are continuously emitted in opposite directions at regular time intervals, every ten nanoseconds. The photons that make up a pair are timed to arrive at the transmitter and receiver at the same time. The transmitter has a switch that directs the first photon between two optical paths. The first path leads the photon to a polarization filter that is oriented with its axis for maximum passage in the vertical direction and the second path leads to a polarizing filter that is oriented in the horizontal direction. The transmitter identifies the detection of a photon that passed through the vertical polarizer as a 1 and one that passed through the horizontal polarizer as a 0. The receiver located on the moon has only one filter that is oriented vertically.
Let's say that there are two detectors, which in the jargon of quantum theory are called Alice and Bob, and they pass messages to each other. Alice is on Earth and she wants to send a message encoded in the four-letter binary code 1001 to Bob on the Moon. The incoming photon reaches the switch in the transmitter and it is transferred to the vertical pole. His discovery forces Bob's photon into a vertically polarized state. The digit was transferred instantly or at speeds ten thousand times faster than the speed of light. When the transmitter wants to send 0 the switch moves the incoming photon to the horizontal pole. Its detection forces Bob's photon into a horizontal position, which is blocked by the polarizer in the receiver: since the receiver expects the next photon in 10 nanoseconds and it doesn't arrive, the receiver detects non-detection as 0. The process continued until all the digits were discovered in a few nanoseconds and in fact the communication is instantaneous and the receiver can also be placed on another galaxy.
The move looks perfect, but unfortunately it can't work, so no one has patented it to date. When Alice's photon passes through the switch in the transmitter it is not automatically routed to a state of vertical polarization. According to quantum theory it has equal probability of vertical and horizontal polarization; And we have no means of predicting in advance what the polarization will be. We can measure the polarization of the photon after the collapse occurs, but there is no way to control which of the two polarizations the photon will acquire during the collapse. Alice who measures and thereby causes the collapse of one photon of the pair of photons in the AP interlacing cannot in any way and by any deliberate means affect the same result that Bob will get when he measures the other photon. Therefore moving Alice's photon to the vertical polarization does not guarantee that Bob's photon will be forced into a vertically polarized state. There is still a 50 percent chance that Bob's photon will pass through or be blocked by the polarizer in his receiver. No message can be passed between Bob and Alice using the quantum entanglement at supersonic speed. The only way is for Alice to inform Bob of the results of the measurement she made and received through a normal and classic communication channel and this limits the communication speed to that of the speed of light.
Jim Baggot, Beyond Measure, Modern Physics, Philosophy and the Meaning of Quantum Theory, Oxford, 2004.
According to the orthodox interpretation of quantum mechanics, the polarizations of the photons are not defined at all before the measurement. At the beginning the two photons are in superposition states of vertical polarization and horizontal polarization. And when the measurement of one photon occurs, only then do the two photons together collapse into a well-defined polarization. Quantum mechanics does not precisely define the polarizations and what the polarizations are for the pair of photons before they are measured. And what's more, quantum mechanics is not ready at all to accept the concept of "defined polarization" of each of the photons in the entanglement as something valid in theory. We can define the correlation between the photons, but not the separate polarization of each photon. Each photon is in a state of interweaving and superposition with the other photon.
Therefore the quantum connection means a new phenomenon. Although it seems that the phenomenon is consistent with the special theory of relativity, which forbids the transfer of information at supersonic speed, but the price is a quantum mystery. Please note that these reasons were obtained from quantum considerations and there are no relativistic reasons and relativistic explanation here.
Now we will focus on relative considerations. Assuming that no message can travel faster than light, if we want to transmit a transmission about how the detectors A and B measuring in the APR experiment will be arranged, we must transmit it before we arrange the experiment so that it arrives on time. We must therefore assume that the direction of the remote detector and the behavior of the remote photon B are determined by events within the past light cone (past cone). But such a theory immediately falls apart because it is hard to imagine that such events in the past would affect photons that are far apart. There is no means by which a sub-light signal and a light signal from the past can provide the information from one side of the experiment to the other. Even if we allow a photon to base its reactions on all the events from its past cone, we will not be able to find a strategy that will restore the quantum correlation. The problem is that in principle the direction of the remote detector B is not determined by the events in the past cone. Let's say we adopt a local deterministic theory (the complete knowledge about the current state of the physical system can be used to determine the future state of the system) or local stochastic; and suppose that no causal effect can propagate faster than light. Even if, say, we examine an event within the cone of the past and explain it according to such a stochastic theory, no such event can have an effect outside the light cone of its future (cone of the future). The events in the past cone can only affect the events in the future cone and not on events that are quasi-spatially separated. Events within the light cone have no direct effect on quasi-spatial events and there is a buffer between the quasi-spatial quantum correlations (having a common cause) and all events within the past cone.
When an entangled state collapses by interacting with one of the two particles, the other particle collapses through a non-local process and superposition represents an indeterminate state (argument against realism) and the collapse to a particular state is a random process (argument against determinism).
Tim Maudlin, Quantum Non-Locality and Relativity, Third Edition, Wiley-Blackwell, 2011.
However, researchers tried to explain the APR experiment by Hugh Ebert's multiple worlds theory which omits the collapse of the wave function according to which there is no collapse of the wave function. Therefore, it is a measurement process and viewers in the interweaving that split into parallel worlds. But in fact the multiple worlds theory is a local theory: splitting into multiple worlds is a local process. Additionally, all options exist in all worlds. If there are researchers who hope that the quantum state represents the "realities" of a photon, the multiple worlds theory moves realism to another place: there is too much realism, there are multiple definite realities. The multiple worlds interpretation also brings back determinism: the wave function develops according to a deterministic wave equation and each possible result of the measurement is realized in its own world. The only problem is that one worldviewer can complain that he got result X and not Y as opposed to what he initially predicted.
We will examine the APR experiment according to the multiple worlds interpretation: the measurement of particle A splits into two through a local process and then splits again. Because there is no wave function collapse, the observer near A has to inform the observer near B of the results of his measurement and then each of them immediately splits - and this happens through a chain of events locally at sublight speed and of course without contradiction with special relativity.
Maybe tachyons, which by definition move at supersonic speed from the start, are able to explain the APR experiment and the violation of Bell's inequalities? Or maybe it is even possible to use tachyons for communication on Orit, another type of Bell phone? Is it possible to send a message or a telegraph from one measurement area in an APR experiment to another using non-local tachyon super-oriental communication?
The problem with tachyons is that different attribution systems may not agree among themselves on the temporal order in which the events occur and therefore on what makes up the past of any event, but still each attribution system is able to put together a story that is consistent with its temporal structure. In signals that travel at sub-light speed, the emission of the signal always occurs before it is received. As for the tachyons moving fast on Orit, in certain reference systems, the reception of the super Orit signal may be before its sending. It means that the signal moves backwards in time, so in these reference systems the result precedes the cause. The temporal order results from the speed of light and the transmission of signals and information in signals. Tachyons cause problems because if used to send messages backwards in time they would have negative energy and therefore create dynamic instability. Do tachyons need to transfer energy to transmit information? Massless photons are confined to the light cone because they carry energy at the speed of light. But if we use a massless tachyon, the energy and momentum of a massless particle on light is zero and such a tachyon can transmit information without energy.
Let's say we manage to neutralize the element that the tachyons move backwards in time by placing some consistent condition. To get the job done, the tachyons have to quickly carry the information on Orit from one side of the APR experiment to the other. Suppose that in an APR experiment in a certain reference system (relative to the laboratory system) when a measurement is performed (we are observing the first photon A), at the exact moment of this observation the photon A sends a tachyon to the second photon B and the tachyon transmits to it the information that must be correlated with the measurement result already performed on the first photon A. That is, the tachyon causes photon B to react accordingly. The technions are therefore "hidden variables". In this situation, it is assumed that the polarizations of the photons are well defined - a realistic assumption - and they are accurately described by the hidden variables. Then in some reference systems this script works. If in a given frame of reference the detection event of the first photon A occurs before the event in which the tachyon meets the second photon B, the sequence of events can be interpreted so that the tachyon is emitted when photon A is observed and swallowed by its partner B just in time to have an effect on its behavior.
But due to the fact that the tachyon is by definition a particle that moves quickly on light there are reference systems in which the tachyon is useless: where the tachyon is emitted by the first photon A before it is measured and therefore it is unable to carry useful information to the second photon B when it arrives at the observation event; And worse, the second photon B emits tachyons at the moment the first photon A is aimed. These correlations between distant photons in spatial-like events are exactly the ones we started with.
In fact, there are also problems in the reference systems where the temporal order is correct: the existence of the tachyon should depend on the way the measurement is performed on the first photon A. There should be a strong correlation between the direction of the measuring device of the photon A and that of the device of the photon B in order for it to receive useful information from the tachyon. That's why a tachyon moving at supersonic speed does not help to solve the non-locality and quantum correlations.
Tim Maudlin, Quantum Non-Locality and Relativity, Third Edition, Wiley-Blackwell, 2011.
If you look at the two-particle correlation system of the APR experiment from the perspective of quantum field theory, you can think of the quantum effects as changing the Minkowski geometry. In 2007, researchers proposed another relativistic hidden variable theory: for the APR model, the quantum effects cause the Minkowski metric to undergo a transformation into a new metric. A geometry is obtained that is effective with two singularities in the hammer and exactly has the pattern of a bridge like a wormhole. In this way, the correlations in the APR experiment can be interpreted as those arising from an effective wormhole that links the two particles in the APR experiment and through which signals are transmitted or propagated - and therefore do not need tachyons. Space-time warps, distance shortens. But such a description misses the non-locality, lack of determinism and lack of realism in the APR correlation.
http://arxiv.org/pdf/quant-ph/0701106.pdf
In 1999 Steven Weinberg proposed a small nonlinear correction to the wave equations of standard quantum mechanics. It turned out that when Weinberg's theory is applied to the correlations between the APR particles, it is possible to transmit an immediate message between the quantum particles in the APR experiment. From this they came to the conclusion that the non-linear quantum mechanics violates causality and APR telephone (communication between non-local observers) is possible. However, Joseph Polchinski showed that the supernatural effects are an error derived from Weinberg's particular formulation and if we include Weinberg's formulation the error will disappear. Researchers immediately appeared who demonstrated: not only is the difficulty of the appearance of super-oric effects unique to Weinberg's formulation, but Polchinsky's recipe for causal non-linear quantum theories that do not contain an effect on oric falls flat.
http://www.everettica.org/art/olch.pdf
http://arxiv.org/pdf/quant-ph/0012041v3.pdf
If so, is relativity violated? The debate continues in the literature. According to the standard consensus in quantum mechanics - we are left with the quantum mystery, a mysterious quantum connection between particles. This is the price you pay not to violate the principles of special relativity. If we try to explain non-local quantum correlations by a hypothetical local and realistic effect, such an effect will have to move quickly on the light and not just, but at an infinite speed.
In contrast to the realistic local explanations that force us to use supersonic transmission, the standard interpretation accepted in orthodox quantum mechanics means that no information is transmitted between one end of an APR experiment and the other; That is, there is actually no conflict between quantum theory and relativity, and this is because observers who are spatially separated (non-locality) in an APR type experiment cannot use their measurement choices and their measurement results to communicate with each other and to pass information to each other. Quantum mechanics even goes so far as to say that realists consider polarization measurements to be the polarization of actual photons. However, the APR experiment can be thought of as a statistical correlation between the measuring instruments only without talking about photons at all, but only about measurements and data...
One of the latest studies in the field at the end of October:
50 תגובות
There will be no zoo 😉
The fourth part answers the questions of the respondents and there was a request from Miron and I am answering this request. All together in the synthesis of a complete essay.
I'm almost certain it was a mouse.
where is he? meow
Will there be something about mice?
Allah is a mouse.
Expecting the best
Now I have also moved to cows!
I see you are cat lovers, you forgot to bring a bowl of milk and cat food 🙂 ….
As they say stay tuned for the fourth part of the quantum philosophy which I hope will answer some of you cat questions. And next time make sure to bring the cat food and water 😉
So see you in the fourth part of the mysterious quantum saga.
jelly
Alright guys, how about this compromise: as long as the box is closed, the cat is in a superposition of alive/dead. Without giving exact numbers like half and half.
What about the claim in the article: "The standard interpretation accepted in orthodox quantum mechanics means that no information is transferred between one end of an APR experiment and the other." Is she correct?
Explain if possible.
Israel,
The development in time is not the main point at all - but the claim that the cat is neither alive nor dead, but both. If it doesn't bother you then you haven't started to understand quanta yet.
Israel,
Quantum theory wonderfully describes the time development of a system - and the results came out in accordance with the classical result (ie 7/8 dead or 3/5 alive or whatever you want) - the point is not half and half!
The point is that in our lives it is difficult for us to understand what a macroscopic system is in superposition, and it does not matter at all how many percentages you give to each state - the very idea that a macroscopic system is in two states at the same time is not clear and accordingly does not receive a very clear definition in the quantum theory according to Copenhagen.
Schrödinger's cat, if they really wanted to go from a dead state to a live state (after the rehearsals)
Got it, the limits of quantum theory. My problem is with the sentence "What is his condition as long as the box is closed? The obvious answer, according to Bohr's method, is: "neither alive nor dead, but half of this and half of that".
http://he.wikipedia.org/wiki/%D7%94%D7%97%D7%AA%D7%95%D7%9C_%D7%A9%D7%9C_%D7%A9%D7%A8%D7%93%D7%99%D7%A0%D7%92%D7%A8
In our neighborhood, a normal street cat, the kind called in the vernacular a cat, after half an hour in the box it was not half alive and half dead, but three quarters alive and only one quarter dead. After 45 minutes he was already five eighths alive and only three eighths dead. Only after an hour he was exactly half alive and half dead.
And with you?
I'll tell you something, I had a time rewind company, I made billions, and after that you'll see dead people resurrected after time rewinds, we'll talk in detail, respectfully blowing water
Israel
Zvi is trying to explain to you that Schrödinger's cat experiment is a thought experiment that comes to test the limits of quantum theory. One of the fundamental problems in quantum theory is the question of measurement. In theory it is not defined what it is
Measurement and what is defined as a measuring device. According to the Copenhagen interpretation there is an inherent separation between the world
The microscopic to our macroscopic world. According to the Copenhagen interpretation, it is not defined what happens during measurement
And what exactly is a measurement? Several questions arose regarding this question: such as does measurement occur in the researcher's mind because we are unable to experience superposition? What is the size (in terms of the number of atoms) of the measuring device?
The Copenhagen interpretation does not answer these questions and Schrödinger's thought experiment came to show that
There is an absurdity in assuming that macroscopic systems can be in superposition. For Schrödinger the absurdity is in a live/dead cat regardless of the smell. According to Schrödinger, it is clear to any reasonable person that there cannot be a cat
alive/dead The standard interpretation does not define when the world becomes quantum and when it is classical. By the way, the multiple worlds theory is apparently an attempt to answer the question. As soon as the experiment is carried out, the world splits into a world where there is a live cat and a world where there is a dead cat, but this interpretation is also not without paradoxes.
Today the challenge is to see if it is possible to produce a live/dead cat in the laboratory, that is, a macroscopic quantum system
In superposition, when will the measurement occur or when will the system not be described by a wave function. Similar to the APR experiment that was initially proposed as a thought experiment and eventually a skin and sinew cream, so even today laboratories around the world are trying to breed Schrödinger cats.
Cats are beautiful
Fix. Not alive/dead but alive (or dead).
deer.
My problem with Schrödinger's thought experiment is that when we open the box we don't just know if the cat is alive or dead - we also know exactly how long it has been dead if it is dead.
In the description of the experiment there is a paragraph: "What is the situation as long as the box is closed? The obvious answer, according to Bohr's method, is: "neither alive nor dead, but half of this and half of that".
But this is not accurate. "As long as" refers to the entire duration of the cat's stay in the box. If the experiment lasts an hour during which the cat is in the box, the probability that the cat is alive decreases as the opening time approaches, and only at the opening moment is it exactly half. In fact, in the first seconds of the experiment, the probability that the cat is alive is close to 100 percent. (True, we can't see it, but we can infer it through logic).
Therefore, the obvious answer to Bohr's method, should be in my opinion: "As long as the box is closed, neither lives nor dies, but lives/dies with a probability that is a linear function of the time that has passed since the beginning of the experiment, divided by the duration of the experiment."
No?
We give the analogy of superposition to dice -
The cube falls again and again backwards and forwards in time.
Each time a different number comes out, but when the cube goes back in time it remembers the number that came out in the previous cycle.
As we look at the cube, it stops repeating in time and the number stabilizes at one result
, the other results disappear and converge to the cube we looked at.
That is, there is one cube that appears many times in time - duplicated and disappears at the end to the number one.
How is this related, for example, to a particle wave and a probe -
A particle repeats again and again, many times and creates a wave in time.
If we give it the possibility to stabilize on several particles at the same time - we get a wave
If we give it the possibility to settle on only one particle - we will get a single particle in the present.
Thanks
.
Israel,
Schrödinger's cat idea is not a quantum experiment, but Schrödinger's attempt to explain through a thought experiment the problematic nature of quantum thinking.
When talking about an atom, electron, photon or any other particle, a person can say to himself:
OK, I've never really seen an electron - so I'm willing to live with the understanding that it's a wave function - from a strange mathematical object that is sometimes a wave and sometimes a particle and it depends on my measurement.
Schrödinger was not satisfied with this interpretation of quantum theory (although he himself was one of its forefathers) and thought that physics itself was still not fully understood. To emphasize the matter, he proposed such an idea:
The fact that we are able to accept a superposition of an electron is due to it being a non-macroscopic object, therefore it is unfamiliar to us and we are ready to accept that things concerning it are not as we know them from everyday life. But if we put a cat in a box with a radioactive atom and a cyanide pill connected to a Geiger counter - we will connect a microscopic object (radioactive atom) to a macroscopic object (cat).
If the atom disintegrated - the cat is dead and if it didn't disintegrate the cat is alive and since according to quantum theory the atom in superposition...
Note,
It is impossible to measure this in an experiment - any such box, when you open it, will contain a live or dead cat - the experiment raises conceptual questions here:
What does macroscopic object mean in superposition?
What determines that a scientist can perform a measurement and a cat cannot?
And if a cat can, what about a cockroach, an ant, a bug or an atom?
The idea of the hidden variables would of course solve the paradox, when the atom went into the box, it had a small label that could not be read and it said "This atom will live for 14 minutes" and that's it - the cat lived for 14 minutes and then died...
So beautiful, so simple - but not true!
Wikipedia holds:
http://en.wikipedia.org/wiki/Quantum_superposition
"The probability of an event can be described by a combination of the probabilities of certain specific other events (see Mathematical treatment). For example, the probability of flipping two coins (coin A and coin B) and having at least one land head-up can be expressed as the sum of the probabilities for three specific events: coin A heads (↑) with B tails (↓ ), coin A heads (↑) with B heads (↑), and coin A tails (↓) with B heads (↑). In this case the probability could be expressed as:
P(heads ≥ 1) = P(A↑ ∧ B↓) + P(A↑ ∧ B↑) + P(A↓ ∧ B↑)”
A cube or a coin is not in 'superposition', it is simply in the air.. In my opinion there is no place for this analogy.
(This is despite the fact that in general I can't really have an opinion on this issue).
Eric.
Each quantum object is in a state of superposition of all possible states before the test. After that he is only in one particular state.
The same goes for a coin, or better perhaps a backgammon cube. It always shows only one side after the fall, but before it it is in a superposition of all 6 states.
With a cat it's a little different, because he always falls on his feet. But it must be assumed that previously he was in the superposition of nine souls.
But I confess that I have never been able to fully understand Schrödinger's cat paradox. True, when we open the box we will find him in only one state, alive or dead. But if he's dead, there's this matter.. how do you say? The fragrance.. that can tell us exactly when he died. So we can know in retrospect exactly when he chose against his own good in this particular situation, and stopped being in superposition. It therefore turns out that the actual opening of the box has no effect, in contrast to the perception of a spinning coin or a spinning cube or the measurement of spin or polarization, which are the causes of the collapse of the wave function and before that the particle was in a superposition of all states.
"2. The coins were in a state of wood wafer superposition before testing, like any coin that is spun in the air before testing. However, as soon as we examined the coin in Jerusalem, it chose, like any other coin, only one condition, wood or straw, and this condition was immediately transferred to his brother in New York. (Quantums, Bohr).”
Israel
I didn't understand your repeated analogy from 'tree and fruit' to quantum theory.
A coin can be at a certain moment in one of more than 2 situations: - just lying on one side or the other or in the air. A cat, on the other hand, can be either alive or dead, there is nothing in between..
A note for waves, it is possible to determine or change the spin if a particle is moved through a charged field or through a polarizer, and this will also cause a possibly partial collapse of the wave function, and this is fundamental for transferring information back in time, and will also affect distant and replicated particles.
My problem is the one-sided view, presenting only Einstein's perception even when you seemingly describe the Copenhagen interpretation.
1. You wrote "What I wrote is that if a photon is measured after it has collapsed, we will say that its polarization is measured after the collapse. There is no way to control which of the polarities will choose at the time of the collapse." According to the Copenhagen interpretation, there is no collapse, at least not physically. The wave function describes the probability that a certain result will be obtained in a certain experiment, the wave function does not describe an actual (real) object and therefore there is no photon
Before it is measured at least not a photon with defined properties.
2. In science, accuracy is important, the claim: the percentage of alcohol in orange juice is lower than 5% is true, but the exact claim is that there is no alcohol in orange juice. My claim was not about the correctness of your claim but about its accuracy.
3. My explanation is again intended to be accurate, I explained that even in the physics that preceded quantum theory it was clear that every measurement changes the measured quantity, the difference is that according to classical physics it is possible to theoretically estimate what the change in the measured system will be as a result of the measurement and therefore it will be possible to estimate what its state was before it was measured . Secondly, I tried to show her that even in the theory of waves there are complementary magnitudes that are not given
For accurate information at the same time and it is still a complete theory.
4.” You wrote "But if we proceed from the assumption that quantum mechanics is a complete theory (the orthodox interpretation of quantum mechanics obtained as a result of the Copenhagen compromise), the measurement on A telepathically changes the state of B (violation of the principle of locality and spheribility), because the change occurs immediately while transferring information quickly infinite and this violates the principle of constancy of the speed of light in the special theory of relativity; and therefore violates the relativity of simultaneity." Now I understand that you meant Einstein's opinion that according to the standard interpretation of quantum theory there is no telepathic transition of anything.
5. Again the issue is accuracy, it is enough to add a sentence explaining why Aspa's experiment was special.
sympathetic,
Philosophy of modern science is my specialty. That's why I called the three articles I published "Philosophy of Quantums" and not quantum physics.
Regarding 1, what I wrote is that if we measure a photon after it has collapsed, let's say we measure its polarization after the collapse. There is no way to control which of the polarizations they will choose at the time of the collapse. By the process of measuring and collapsing one photon from the pair of photons in the interlacing in the APR experiment, it is not possible to influence the result obtained in the measurement of the second photon. Therefore the collapse of the wave function is a process that cannot be controlled.
Regarding 2, it is not clear what the correction is: I said that the position of that particle cannot be known with a probability of 1 and you said that the probability of knowing the position of the particle is 0. That is, I used negative language and you used positive language. And so we both said the same thing.
Regarding 3 - I brought the description of Einstein, Podolsky and Rosen from 1935. Do you want to argue with Einstein? Einstein thought that quantum mechanics was incomplete and the uncertainty principle bothered him, so he proposed the APR experiment. What you write annoys the physics books. It is known that Einstein opposed quantum mechanics, so if you argue with Einstein and bring today's interpretation of quantum mechanics, you will obviously correct him.
I just added on Einstein an explanation for realism: "The measurable characteristics of the physical system exist and are well defined separately from any external influence and observations". If you don't like this definition, I'm open to suggestions for other definitions.
Regarding 4. Again you are trying to change Einstein's APR article from 1935. Einstein complained about there being a telepathic transition between the particles because he was a realist!! And that's why he was so frightened and uttered his famous saying "Action at a distance of ghosts"! It is clear that Niels Bohr, for example, would say the opposite of Einstein...
Regarding 5, the article is not in the history of science. The article is in the philosophy of science. In principle, when writing a philosophy of science, you combine the history of science with the philosophy of science in order to be precise in the details - for example, when I described the APR experiment, I used the history of science to distinguish between three versions of the APR experiment: Einstein's, that of Boehm and Bell's. But when there is no need and you write an article in the philosophy of science, then you don't use the history of science, which is why I only mentioned the Alan Espa experiment and I didn't elaborate on the experiment because the article does not deal with the experimental aspect of quantum entanglement, but with the theoretical aspect.
Flowing with you, water. I still don't understand where the complication is.
For example, the hidden variables do not comply with causality and locality (perhaps it is not written most clearly in the wiki, forgive the wiki)
Water, can you explain what "a bit complicated" is in Hebrew?
Robbie, again as far as I understand the response in negative time comes between the test and the cracks and if you try to see after - you wasted the negative time
And Israel, it got a little complicated (gently, yes)
jelly.
A. In the bottom line, it is possible to summarize the issue of non-locality in quantum entanglement into two coins that have been separated, one is now in Jerusalem and the other in New York. If you check one of them and see that it is resting on a tree, so is the other. With on Peli, as above. This is the case with every test we do for coins.
My logic (and I believe Einstein's and Bohr's) says that there are two possibilities:
1. The situation was predetermined even before the separation between the currencies. (Hidden variables, Einstein).
2. The coins were in a state of superposition of wood and wafers before the test, like any coin that spins in the air before testing. However, as soon as we examined the coin in Jerusalem, it chose, like any other coin, only one condition, wood or straw, and this condition was immediately transferred to his brother in New York. (Quantums, Bohr).
However, it is clear that in the example of the coins, if option 2 is correct, the information about the state of the currency had to pass immediately from currency A to currency B at time 0.
If we return to intertwined particles, we can of course say that the two particles are actually one, so there is no problem here. But this only complicates the situation: if the same particle is in two distant places at the same time, how does the information about the collapse pass from one end of it to the other?
And since Bell and Assembly proved that Bohr was right, it is clear that the information about the state of the particle passes immediately to its entangled brother.
Is there another explanation for the coin pattern?
Is there a fundamental difference between the coins and entangled quantum particles?
And if the answer to the 2 questions is no, there is no escaping the conclusion that information passes at time 0 from one particle to another.
No?
B. It can be logically proven that if any speed, not necessarily that of light, is the same for every measurer, sending information above this speed violates the principle of causality. This is why the speed of light is considered the upper speed limit.
In Wikipedia under the EPR paradox it is stated that this was the claim of Einstein and his friends against the integrity of quantum mechanics, that information in entanglement exceeds the speed of light and therefore is not possible.
Einstein was proven wrong. Hidden variables do not exist, and quantum theory won (true, only as far as we know. If the old fox had lived, he would probably have found some way out of the tangle, as always. But that's not related).
So how come they didn't give up on relativity? After all, it has been proven that information travels faster than light and that Einstein was wrong.
The explanation is a bit convoluted: indeed, information about the spin or polarization passes instantly - but this does not mean that information can be sent faster than light (as suggested by Ruby). We cannot send even the most basic information - up or down - through quantum entanglement, so there is no contradiction to relativity here.
good and beautiful But all these data were also before Einstein in 1935 - so why did he say non-locality contradicts relativity? What, we understand relativity better than Einstein?
It turns out that the maestro was wrong twice in EPR - the first time when he claimed that there are hidden variables and there is no non-locality, and the second time when he claimed that non-locality contradicts relativity.
third. Permission question - as I already asked in the first and second articles: Can the Wheeler experiment be interpreted in a different way than an influence from the present on the past? An explanation that would go well with what we know about quantum mechanics?
Moti,
Yes, that's what I mean.
But to be completely honest, I don't think there will be any change in the pattern of interference on the other side...
I am sure that the results of the EPR experiment go beyond a very fundamental problem and are too easily solved by me
The tendency to load a bit of information on a photon - and make life easy.
Hence my thought experiment, taking the wave function and loading it with a bit of information
Then all the "doesn't contradict" relativity arguments go kaput.
If in my thought experiment the girl in the other galaxy sees a change in the interference pattern, it can be transferred
Information at a speed that exceeds the speed of light.
If she sees nothing, something in the definition of photon entanglement and wavefunction collapse is defined
Incorrectly in quantum mechanics.
I'm pretty sure that both relativity and quantum mechanics are a very accurate picture of a particle
from physical reality, but the dissonance of both indicates their inclusion in theory much more
large and precise, and perhaps even on fundamental changes of our basic definitions regarding physical reality
That is, matter/energy/space and time...
By the way, I would also like to know the author of the article
Good Day
Ruby
And another note to Ehud, can you expand on the difference between a situation where there is a chance for two situations and the possibility that there is one situation but we don't know which one it is? And the connection of this that is requested to transfer information back in time? , (also in the classical prose)
Note to Ehud, because you go down in the dimension of the space, you can transfer partial information again not with certainty but information, something passes, and you can multiply it to gain more knowledge back in time, for example even from 30% yes logically you can transfer information
A beautiful and important article, but unfortunately it contains many inaccuracies, several corrections:
1. "According to the orthodox interpretation of quantum mechanics, this is not under our control. The collapse of the wave function is an immediate process and independent of the spatial separation between the two particles."
According to the orthodox interpretation of quantum theory it is only possible to talk about possible results of a measurement, before the measurement there are no two particles in two different places, there is no meaning according to the orthodox interpretation to talk about realities that are not the result of a measurement. One must be careful about this concept, especially in an article that tries to describe the philosophical side.
2."So if the momentum of a particle is known with a probability of 1, we cannot know with a probability of 1 the position of that particle." The situation is worse if we know with a probability of 1 the momentum of the particle we have no information about its position which means the probability of knowing the position of the particle is 0.
3. "As a result of Heisenberg's uncertainty principle, incompatible quantities cannot be determined with certainty. It seems that this violates the sufficient condition for the realism of a physical quantity, according to which a physical quantity can be predicted with certainty without disturbing the system - (or the measurable characteristics of the physical system exist and are well defined separately from any external influence and observations). Therefore, if according to the uncertainty principle it is not possible to predict a quantity with absolute certainty, quantum mechanics is incomplete." In wave theory, it is not possible to produce a narrow wave packet so that it is spatially located and still determine with certainty the wave number of the group, and yet wave theory is still a physical theory. Second, every measurement of a physical quantity changes it, the assumption in realism is that it is possible to theoretically take the disturbance limit to zero and it is possible to determine what the physical quantity was before we measured it. For example, measuring a charge by bringing a test charge closer to it changes the charge distribution, but if we take a smaller and smaller test charge, we can calculate what the charge distribution was before we brought the charge closer.
4. "But if we proceed from the assumption that quantum mechanics is a complete theory (the orthodox interpretation of quantum mechanics obtained as a result of the Copenhagen compromise), the measurement on A telepathically changes the state of B (violation of the principle of locality and spheribility), because the change occurs immediately while transferring information quickly infinite and this violates the principle of constancy of the speed of light in the special theory of relativity; and therefore violates the relativity of simultaneity." Again according to the Copenhagen interpretation there is no telepathic transition between the particles, it is simply not possible to talk about particles and their state before the measurement, it is only possible to talk about the possible results of a measurement.
5. "The version of the Bell experiment, an experiment (EPRB), was carried out in the laboratory by Alan Espa and the predictions of quantum mechanics were confirmed." Alan Espa was not the first to perform the experiment, there were several experimenters who performed similar experiments. What is special about Aspa's experiment is the test of changing the direction of the polarizers after the photons have left the source.
And regarding the cat from above - if he is in a super position and he feels a stab on one side, after the collapse or time reversal he can feel in his life the sharp but transparent pain, depending on the force of the reversal and what you are positioning yourself for, get it from experience, humor
Photons have a connection in the past even though they are far away, and if one is "dropped into a selected state" through its connection with its "distant self" only replicated in time, through the beginning of the duality - back in time, information passes through to all replications of the particle, just not absolute - partially, statistically, affected , transferring and more
blowing water,
What I answered above for Israel. You say that the particle moves backwards and forwards in time many times and therefore it knows and remembers, is affected, by what it does far away and on the other side and therefore it transmits statistical information.... Affected by the future of impact, the future of speed.
In quantum entanglement the particle cannot move backwards and forwards in time many times. This is a non-local phenomenon. If we look at the space-time diagram. The entangled photons are outside the light cone. When they say "knows and remembers" they mean the trajectory of a particle that is inside the cone of light; Its trajectory moves from the cone of the past to the cone of the future. Here there is an immediate action of two distant photons that have no communication between them. You make a measurement and it immediately causes the two photons to collapse together to specified values - even if the two photons are one on Earth and the other in the Andromeda galaxy. This is a quasi-spatial separation. There is no transfer of information here at all between the two photons and there is no influence from the past nor from the future.
Israel,
Answers:
Let's say there is a quantum entanglement between two distant particles, photons in a superposition of vertical and horizontal polarization. Before the measurement was performed the polarizations are not defined at all. It's like Schrödinger's cat. Before peeking into the box, the cat's condition is not defined at all. Only as soon as you peek into the box is there a collapse of the wave function. And regarding the entangled photons, only when a measurement is made with one photon, the two photons together collapse to a defined polarization. You don't know what the polarizations are before they are measured, but only after they are measured. And so since the two photons together collapse into a defined polarization - even if they are light years apart! - No information is transferred from one photon to the other. This is the quantum mystery.
Einstein saw in this situation a contradiction to special relativity: if two photons collapse together in this way, then this is a violation of the relativity of simultaneity in the theory of special relativity. In addition, Einstein was a realist. The realist looks for "hidden variables", which are reasons behind things. The interpretation I gave above is an extension of Niels Bohr's Copenhagen Consensus. In the article above I explained Einstein's objection. Those who came later actually divided into two groups:
One, like Einstein, tried to find theories of hidden variables (like the tachyons) that tried to explain that there is actually some mysterious telepathy between the two photons that is transmitted by particles or signals on light. This is an APR phone or a Bell phone.
And the second went with the standard interpretation of the quantum theory that I brought here in the answer and it grew out of the Copenhagen compromise.
As I wrote here in the article, we need to differentiate between several concepts:
Realism, locality and non-locality and determinism. Einstein was a realist, his special theory of relativity is local and deterministic. The interpretation of the multiple worlds is local because it eliminates the collapse of the wave function and realizes all the options in parallel worlds.
By the way, Niels Bohr answered Einstein's APR argument in 1935 by reformulating his APR experiment in the form of a two-slit experiment.
Ruby,
If you mean the transfer of information based on the change in the interference pattern (0 logical has an interference pattern, 1 logical has no interference pattern) - sounds interesting. In any case, you need some putans to define a situation.
There is a fundamental barrier to classical information, it seems. See also:
http://en.wikipedia.org/wiki/Quantum_teleportation
Or in Hebrew:
http://he.wikipedia.org/wiki/%D7%98%D7%9C%D7%A4%D7%95%D7%A8%D7%98%D7%A6%D7%99%D7%94_%D7%A7%D7%95%D7%95%D7%A0%D7%98%D7%99%D7%AA
Lamuti:
The question in my experiment and leave for the moment subtleties of an experiment
The mother is in a distant galaxy while the guy is on earth
Playing with the switch with the options with metering/without metering
Does the girl in the other galaxy see a change in her interference pattern
Yes or no and why not...
It is clear that the wall is also a type of measurement... but that is not relevant
And to make it easier, think that the Earth and that galaxy are exactly the same distance
from the photon shooter and that the distance between the partitions and the wall is an astronomical distance...
So that, from a statistical point of view, a measurement is being made on a partition in the earth
The photon entwined in the other galaxy has not yet reached the wall and therefore its function has not collapsed 🙂
What does the girl in the galaxy far away see? Does the pattern flash before her eyes
Or nothing happens...? (Remember: she does not measure if her photon passed through any partition)
Ruby
It will be possible in the future to cancel / influence statistical information, in short to play with it
Which is pronounced between the measurement and the cracks, Bassa? ? ?
Ruby
In any case there will be a crash, in a wrestling pattern there is also a crash and it happens on the screen.
If a measurement is performed, as we know, there is also a collapse, and this happens in a crack.
Roughly, yes, that's the intention, something with negative time, you just need a game about the time difference
Another thought experiment:
Two entangled photons are fired every 10 nanoseconds
They arrive at the two crack experiments of quantum mechanics
One on Earth and the other in the other galaxy...
In the meantime, no measurement has been made as to which crack the photons pass through,
Therefore, at this given moment, conflict patterns are obtained
both on earth and in the other galaxy
Now Bob (?) on Earth measures if the photon passed through partition 1 and factors
For the collapse of the wave function both on Earth and in the other galaxy (this is the idea of quantum entanglement isn't it?)
and causes that the interference pattern in the experiment on Earth disappears and in its place appears a statistical dispersion of
The impact of the photons that passed through one of the partitions (doesn't matter which one).
Susie who had not measured anything should now, out of nowhere, see the pattern of interference reverse
for the statistical dispersion of the photons' impact...
Now Bob, flipping the Earth measurement switch over and over
and signals to Susie in Morse that Robbie has invented communication at a speed that exceeds the speed of light
Or alternatively...Suzy calls on a normal phone (waits a long time) and informs Bob, which probably isn't really
We understood what a wave function collapse is, what a particle is and how the universe is built
Because she still sees a pattern of struggle on her side...
: )
What is the "mystery" here - the particles move back and forth in time many times, and a particle that returns feels, knows, remembers, is affected by what it did far away and on the other side, therefore it transmits statistical information and is affected accordingly, and there is also the "idiocy of a "constant" speed, constant because it knows in advance what it will hit and at what speed, the speed of "light" also has information transmission faster than the speed of light, because it is affected by the future of the impact, the future of the speed - constant speed, knows in advance at what speed it will hit, and this is also from the movement backwards and forwards in time of the particles .
jelly
In the last paragraph below it is written "the standard interpretation accepted in orthodox quantum mechanics means that no information is transferred between one end of an APR experiment and the other".
No information is transmitted from Zimmerat? After all, before the measurement the two particles are in a superposition of 2 states, after which the states are correlated. So how did information not pass?
And if non-locality in quantum entanglement does not contradict relativity and the principle of non-transfer of information quickly over time - why did Einstein say that such a contradiction exists? What do we see that he did not see? After all, all the data was in front of him in 1935 as well.