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Quantum Mechanics
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from https://www.thoughtco.com/what-is-schrodingers-cat-2699362 Erwin Schrodinger was one of the key figures in quantum physics, even before his famous "Schrodinger's Cat" thought experiment. He had created the quantum wave function, which was now the defining equation of motion in the universe, but the problem is that it expressed all motion in the form of a series of probabilities—something which goes in direct violation to how most scientists of the day (and possibly even today) like to believe about how physical reality operates. Schrodinger himself was one such scientist and he came up with the concept of Schrodinger's Cat to illustrate the issues with quantum physics. Let's consider the issues, then, and see how Schrodinger sought to illustrate them through analogy. The quantum wave function portrays all physical quantities as a series of quantum states along with a probability of a system being in a given state. Consider a single radioactive atom with a half-life of one hour. According to the quantum physics wave function, after one hour the radioactive atom will be in a state where it is both decayed and not-decayed. Once a measurement of the atom is made, the wave function will collapse into one state, but until then, it will remain as a superposition of the two quantum states. This is a key aspect of the Copenhagen interpretation of quantum physics—it's not just that the scientist doesn't know which state it's in, but it's rather that the physical reality is not determined until the act of measurement takes place. In some unknown way, the very act of observation is what solidifies the situation into one state or another. Until that observation takes place, the physical reality is split between all possibilities. On to the Cat Schrodinger extended this by proposing that a hypothetical cat be placed in a hypothetical box. In the box with the cat we would place a vial of poison gas, which would instantly kill the cat. The vial is hooked up to an apparatus which is wired into a Geiger counter, a device used to detect radiation. The aforementioned radioactive atom is placed near the Geiger counter and left there for exactly one hour. If the atom decays, then the Geiger counter will detect the radiation, break the vial, and kill the cat. If the atom does not decay, then the vial will be intact and the cat will be alive. After the one-hour period, the atom is in a state where it is both decayed and not-decayed. However, given how we've constructed the situation, this means that the vial is both broken and not-broken and, ultimately, according to the Copenhagen interpretation of quantum physics the cat is both dead and alive. Interpretations of Schrodinger's Cat Stephen Hawking is famously quoted as saying "When I hear about Schrodinger's cat, I reach for my gun." This represents the thoughts of many physicists, because there are several aspects about the thought experiment that bring up issues. The biggest problem with the analogy is that quantum physics typically only operates on the microscopic scale of atoms and subatomic particles, not on the macroscopic scale of cats and poison vials. The Copenhagen interpretation states that the act of measuring something causes the quantum wave function to collapse. In this analogy, really, the act of measurement takes place by the Geiger counter. There are scores of interactions along the chain of events—it is impossible to isolate the cat or the separate portions of the system so that it is truly quantum mechanical in nature. By the time the cat itself enters the equation, the measurement has already been made ... a thousand times over, measurements have been made—by the atoms of the Geiger counter, the vial-breaking apparatus, the vial, the poison gas, and the cat itself. Even the atoms of the box are making "measurements" when you consider that if the cat falls over dead, it will come in contact with different atoms than if it paces anxiously around the box. Whether or not the scientist opens the box is irrelevant, the cat is either alive or dead, not a superposition of the two states. Still, in some strict views of the Copenhagen interpretation, it is actually an observation by a conscious entity which is required. This strict form of the interpretation is generally the minority view among physicists today, although there remains some intriguing argument that the collapse of the quantum wavefunctions may be linked to consciousness. (For a more thorough discussion of the role of consciousness in quantum physics, I suggest Quantum Enigma: Physics Encounters Consciousness by Bruce Rosenblum & Fred Kuttner.) Still another interpretation is the Many Worlds Interpretation (MWI) of quantum physics, which proposes that the situation actually branches off into many worlds. In some of these worlds the cat will be dead upon opening the box, in others the cat will be alive. While fascinating to the public, and certainly to science fiction authors, the Many Worlds Interpretation is also a minority view among physicists, though there is no specific evidence for or against it.
Quantum mechanics is every Hollywood writers favorite handwavy tool to accomplish whatever they feel like in a given moment regardless of whether what they say or have happen has anything remotely to do with the reality of this branch of science and, well, reality. Beyond the masses, it is so NOT understood that even the likes of Richard Feynman, one of the greatest theoretical physicists said (probably joking) that nobody understood the topic. And yet, many will use examples to explain it, and probably there’s no example that is used more often than Schrödinger’s cat… but don’t do it yourself, because chances are that you are missing the point Schrödinger intended. For the uninitiated, in an ironically oversimplified nutshell, quantum mechanics is the study of everything at a very small scale - this includes the study of elementary particles such as the ones that constitute an atom. The realm of quantum mechanics is largely probabilistic, given that things that seem so simple in classical physics such as knowing the position and momentum at the same time of macroscopic objects is impossible at the scales of an atom or smaller. Quantum mechanics therefore deals with superposition states, where a particle could be in more than one state at a time before it is forced to collapse when observed. As you can imagine, this is not an easy pill to swallow and at the infancy of this branch of physics everyone was struggling to get some water fast. A lot of proposed different solutions have been published explaining the lack of deterministic nature from these very small particles, yet no one has been able to offer one that is universally accepted. Many physicists are actually content with just dealing with the probabilistic mess since it has worked so far. Albert Einstein was not among them. So he, along with Boris Podolsky and Nathan Rosen published a paper in 1935 called “Can Quantum-Mechanical Description Of Physical Reality Be Considered Complete?” where they claimed that quantum physics was not complete due to the paradoxes it could create without any further context. As an example, they mentioned in the paper the issue regarding quantum entanglement; the phenomenon of how a particle’s state could influence another one even if they were separated, regardless of distance, yet this influence would be instantaneous. According to Einstein, this would mean that information would be traveling at infinite speed, therefore breaking one of the most fundamental constants of physics; the speed of light. In 1964, John Stewart Bell proposed a solution for the paradox and later experiments supported these conclusions, but at the time of Einstein’s article, another physicist was not impressed either with the implications that quantum indeterminacy brought to the table, and that someone was Erwin Schrödinger. Born in Austria in 1887, Erwin Schrödinger was not only a successful physicist, but also contributed to quantum mechanics significantly and one of these contributions was the Schrödinger equation, which is used to describe the wave function of a system, a tool that would eventually earn him a Nobel Prize in physics that he shared with Paul Adrien Maurice Dirac. Given that his career has been so extensively dedicated to quantum mechanics, you might wonder; how could he be skeptical of quantum mechanics’ description of nature? To answer this, it is necessary to dive into the conversations Schrödinger and Einstein had through the years. Given their shared skepticism of quantum indeterminacy, they would exchange letters about the topic and in one of these letters he proposed an example that is fairly known by everyone at this point: Imagine a cat inside a steel box, inside with the cat there is a device; A geiger counter (a device to measure radiation) is monitoring a small amount of a radioactive substance with a probability of 50% that one of the atoms would decay in the next hour (of course with a 50% chance that no atom will). If one of the atoms decay, it will be detected by the Geiger counter, which will tell the device to release hydrogen cyanide. Given the vague nature of quantum mechanics, until measured or observed, the system has not been forced to collapse into one of two states (the atom decaying or not decaying), therefore the cat is equally just as dead and alive at the same time as the atom is decayed or not decayed, since the cat’s health is dependant of the mentioned atom. The trigger that will force the atom and subsequently the cat into one of the two possible states is a physicist (hopefully not the owner of the cat) that will open the door of the box and look by himself after an hour the experiment has started. You see, the problem the physicist had with quantum mechanics was that no one knew where its probabilistic effects ended. Why would the life or death of the cat be dependent on our observation? Why would the system care if we observe it or not? Isn’t the cat observing the poison? Who is observing the physicist observing the inside the box? How large could these probabilistic effects be? If it has a limit in its scale, how large is it? How could a system be independent and superpositioned before our observation but then its state be defined only once we observe it? This is a mess to explain because in relative macroscopic terms, everyday objects are not in multiple states until an observer interacts with it. It is therefore illogical that before opening the box, the cat is dead and alive at the same time, and only until you open the box the cat is retroactively dead, if that’s the result observed. This was meant as a direct critique of the Copenhagen interpretation. Einstein couldn’t agree more with the implications this scenario created. When amplifying its effects, the situation regarding what is deterministic and what is probabilistic becomes very hard to define. Stating this in a letter sent to Schrödinger in 1950: This interpretation (that quantum mechanics is a complete description of reality) is, however, refuted, most elegantly by your system of radioactive atom + Geiger counter + amplifier + charge of gun powder + cat in a box, in which a psi-function of the system contains the cat both alive and blown to bits. Is the state of the cat to be created only when a physicist investigates the situation at some definite time? Nobody really doubts that the presence of absence of the cat is something independent of the act of observation. But then the description by means of the psi-function is certainly incomplete… It must be said that it was Einstein who substituted the cyanide for gunpowder as a means of hypothetical animal cruelty. Naturally, the thought experiment has been either misquoted and even sometimes twisted to prove something unrelated to physics entirely. The easiest misconception to make about the thought experiment is that Schrödinger was serious about this experiment, and that “it could be done”. You might have guessed at this point that he didn’t take the concept seriously, rather he mocked the possibilities that quantum indeterminacy implied. Another misconception is the favorite from philosophers and people who want to give a mystic nature to this thought experiment. For them “observer” is defined as an actual “eyewitness”, so to speak; a conscious entity or a person. This normally branches into linking consciousness and quantum mechanics in a very holistic way to give mystic-like philosophies some kind of credibility. One famous theory is the Von Neumann-Wigner Interpretation that claims that consciousness is necessary to collapse the wave function. It must be pointed out however that Schrödinger probably meant that either an observer could be or not be a conscious observer. It could be something that simply measures or interacts with the system. So its philosophical reach probably was not meant to necessarily speak about conscious beings or even point out that a conscious observer was not necessary. Physicists tend to lower the role of a conscious actor in the model, since for them, the universe does not care for your interpretation. A very simplified interpretation was that Schrödinger was mocking or dismissing quantum mechanics entirely. But knowing that he established very well known formulas and that everyone knew that quantum mechanics works, this is not the case at all. He just simply argued that instead of interpreting quantum mechanics as a complete theory that relies on probability, that we might just not know how the real gears behind it works. As science author Philip Ball, pointed out, Erwin Schriodinger did not mean to say that quantum physics are not applicable to everyday macroscopic objects. We already know about this, but rather use the example as an absurd, exaggerated way to show that pushing the limits of what could be considered as “quantum objects” could bring paradoxes that might not be easily solvable. Of course, that hasn’t stopped people from trying. For example, we have the relational interpretation which states that anything can be an observer, each with their own version equally valid: If the cat has been poisoned, it observed the system collapsing, but since the physicist has not looked inside the box, the system is in superposition for him, until he obtains more information about it by opening the box. There is also the Many-Worlds interpretation by Hugh Everett, where it says that any measurement that forces a system to collapse into one of two superpositioned states, will split reality in two; both equally real, and yet, none can interact with each other. This means that the collapse never happened: if you open the box and the cat is still alive, it was always meant to be alive… in your reality, but now there’s another universe where you are being arrested with charges of animal cruelty. As for Neils Bohr, the main antagonist of Albert Einstein regarding this topic, the riddle wasn’t a riddle at all. He didn’t think the observer directly triggered the collapse, it simply measured it. For him, the first observer was the Geiger counter. One could say that for Bohr, anything outside the box was not necessary to obtain a result. Many more solutions to the paradox have been proposed, at the same time showing only how hard it is to solve. None of these have offered a satisfactory conclusion for everyone. This is probably why Erwin Schrödinger wasn’t much of a fan of speaking about probability in quantum mechanics, stating: I am no friend of probability theory, I have hated it from the first moment when our dear friend Max Born gave it birth. For it could be seen how easy and simple it made everything, in principle, everything ironed and the true problems concealed.
from https://byjus.com/jee-questions/what-is-schrodingers-cat/ What is Schrodinger’s cat?. Schrodinger’s cat is not a physics theory or a real experiment. It was just a teaching tool or an imaginary experiment used by Schrodinger to show how some people misinterpreted quantum theory. It was sometimes described as a paradox. In this imaginary experiment, Schrodinger placed a cat in a box along with a radioactive substance, a hammer and Geiger counter and a vial of poison. When the radioactive substance kept in the box decays, the Geiger counter will detect it and will trigger the hammer to release the poison. This will subsequently kill the cat. It is not possible to predict when radioactive decay will happen since it is a random process. An observer will not know if the cat is dead or alive until the box is opened. The cat’s fate is tied to whether the radioactive substance has decayed or not and the cat would be, as said by Schrodinger “living and dead…. in equal parts” until the box is opened to observe the cat. In simple words, the state of the cat will be completely unknown till it is observed, so till the box is opened the cat is both dead and alive, a state known as quantum superposition. The state of superposition applies to the random subatomic event, that may or may not occur. Nobody knows the state of the subatomic particle until it is observed.
from https://www.worldatlas.com/what-is-schrodinger-s-cat.html Schrödinger's cat is a concept that was deliberately created by a physicist from Austria, Erwin Schrödinger, as a counterstatement to Copenhagen's interpretation of quantum mechanics. In his experiment, which fortunately for all the feline species remained on a thought level only, the cat can be both alive and dead when certain experiment factors are deconstructed. Why did Schrödinger develop this thought construct in the first place? In 1935, he critiqued the way quantum mechanics scientists were explaining the state of an object. From the so-called Copenhagen interpretation, an object is able to exist in all possible configurations within a specific period. However, if we extrapolate that system to observation, all other options collapse, and we can see only one possible state of an object. How did Schrödinger approach this problem? Well, he told people to imagine an experiment that involves: a cat, a bottle of poison, radioactive material, the Geiger counter, and a hammer all inside one box. The way he set up the rules is essential to understand the paradox that comes out of the possible results. The amount of radioactive material inside the box is so small that there is only a 50% chance that the Geiger counter would detect it in 60 minutes. If radiation was recognized, the hammer would fall and smash the bottle of poison, thus killing the cat. Schrödinger claimed that, until we open the box and see what actually happened, the cat is both dead and alive. When an object takes that form, it is called a superposition. Of course, this was enough to point out the paradox that occurs in Copenhagen's explanation. The paradox is contained in the fact that the cat cannot be both alive and dead at the same time, and Schrödinger applied the whole critique to how quantum mechanics scientists offered their explanation. Schrödinger's Concept Does Not Prove Anything This experiment Schrödinger explained, in its essence, is not a legitimate one and did not actually prove anything. The Schrödinger's cat concept was used merely as a mechanism to explain the problems in interpretation quantum mechanics was having as a field. This kind of thinking was further embellished by Albert Einstein, who not only agreed with Schrödinger's explanation but extended the critique even further, asking the question: is the state of an object created only when it is under investigation at a specific moment? From that period, there have been enough advances in the way quantum mechanics explain the state of an object. Now, it is documented how a quantum particle can collapse in almost any kind of interaction. Put shortly, together with Einstein, Schrödinger has implemented a fundamental view of thinking in modern science; the one which suggests that the change in state can come in many other ways, and not only when performed by a conscious observer, or a scientist. However, the theory in which the truth is in the eye of the observer is still very much used by scientists that take part in writing and thinking about filling the popular science category on the bookshelves. from https://www.lovecatstalk.com/what-is-schrodingers-cat-explained/ “Schrodinger’s Cat” was not a real experiment and therefore did not scientifically prove anything. Schrodinger’s Cat is not even part of any scientific theory. Schrodinger’s Cat was simply a teaching tool that Schrodinger used to illustrate how some people were misinterpreting quantum theory. Schrodinger constructed his imaginary experiment with the cat to demonstrate that simple misinterpretations of quantum theory can lead to absurd results which do not match the real world. Unfortunately, many popularizers of science in our day have embraced the absurdity of Schrodinger’s Cat and claim that this is how the world really works. In quantum theory, quantum particles can exist in a superposition of states at the same time and collapse down to a single state upon interaction with other particles. Some scientists at the time that quantum theory was being developed drifted from science into the realm of philosophy, and stated that quantum particles only collapse to a single state when viewed by a conscious observer. Schrodinger found this concept absurd and devised his thought experiment to make plain the absurd yet logical outcome of such claims. Is The Cat Dead Or Alive In The Box The thought experiment gets to the philosophical heart of quantum mechanics. In one easy-to-understand scenario, the potential issues with the Copenhagen interpretation are laid bare and proponents of the explanation are left with some explaining to do. One of the reasons its endured in popular culture is undoubtedly that it vividly shows the difference between how quantum mechanics describes the state of quantum particles, and the way you describe macroscopic objects. However, it also tackles the notion of what you mean by measurement in quantum mechanics. This is an important concept, because the process of wave function collapse depends fundamentally on whether something has been observed. Do people need to physically observe the outcome of a quantum event, or does it simply need to interact with something macroscopic? There isn't really an answer to these questions thats widely-accepted. The paradox perfectly captures what it is about quantum mechanics that is hard to stomach for humans accustomed to experiencing the macroscopic world, and indeed, whose brains ultimately evolved to understand the world in which you live and not the world of subatomic particles. Schrödinger’s cat is a thought experiment, usually described as a paradox, devised by Austrian physicist Erwin Schrödinger in 1935. It illustrates what he saw as the problem of the Copenhagen interpretation of quantum mechanics, applied to everyday objects. Stephen Hawking is famously quoted as saying “When I hear about Schrodinger’s cat, I reach for my gun.” This represents the thoughts of many physicists, because there are several aspects about the thought experiment that bring up issues. The biggest problem with the analogy is that quantum physics typically only operates on the microscopic scale of atoms and subatomic particles, not on the macroscopic scale of cats and poison vials. The Copenhagen interpretation states that the act of measuring something causes the quantum wave function to collapse. In this analogy, really, the act of measurement takes place by the Geiger counter. There are scores of interactions along the chain of events it is impossible to isolate the cat or the separate portions of the system so that it is truly quantum mechanical in nature. Whether or not the scientist opens the box is irrelevant, the cat is either alive or dead, not a superposition of the two states. Still, in some strict views of the Copenhagen interpretation, it is actually an observation by a conscious entity which is required. This strict form of the interpretation is generally the minority view among physicists today, although there remains some intriguing argument that the collapse of the quantum wavefunctions may be linked to consciousness. Why Schrdinger Put His Cat In The Box And Why It May Never Get Out Long before cats conquered the internet, two of the greatest physicists of our time Erwin Schrödinger and Albert Einstein devised what almost seems like an evil thought experiment. Schrödinger developed the scenario in a discussion with Einstein in response to misinterpretations of quantum mechanics at the time. It was a way to describe how a concept that seemed to apply to minute electrons in atoms might apply to a complex object in the macroscopic world in this case, a cat. Schrödingers cat experiment was hypothetically used to show [that] Schrödinger disagreed with the Copenhagen Interpretation for larger objects, like a cat. Schrödinger’s thought experiment was designed to show what the Copenhagen interpretation would look like if the mathematical terminology used to explain superposition in the microscopic world was replaced by macroscopic terms the average person could visualize and understand. In the experiment, the observer cannot know whether or not an atom of the substance has decayed, and consequently, does not know whether the vial has broken and the cat has been killed.
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