# Tag Info

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Some history here might be useful; one of the oldest cosmological theories that we have was developed by Ionian philosophers which was an atomic theory; in that theory uncertainty as in random motion was taken as something fundamental (they called it the clinamen which is usually translated as swerve). This shows that pure determinism, physically, is ...

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The Heisenberg Uncertainty Principle (HUP) holds for special observables, as energy and time, space and momentum, .. To every observable there corresponds a quantum mechanical operator. Quantum mechanical operators either commute or not commute, and are seen in the commutation relationships. Observables that do not commute are what the HUP is about. Is ...

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First and foremost we have to understand that if we are deriving laws of nature then our primary assumption is that the natural phenomenons are not random. If they are random, it would be impossible to say anything about them. Now let's come back to Quantum Mechanics. There is nothing random about the motion of electrons or any other subatomic particles ...

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There is something going on. Which is that certain observables are fundamentally incompatible. That means firstly that you can do an experiment for one observable or for another observable, but you can't do an experiment for both observables at the same time. And what's worse if you did an experiment for A then one for A again and then one for B the two ...

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Out of the many quantum-mechanically possible states of an oscillator (be it a mechanical one or light waves), the ones we almost exclusively observe are the coherent states. In a way, they are the states where uncertainty is evenly distributed, such that every uncertain quantity scales as $\sqrt{N}$ for $N$ quanta (e.g. photons or energy quanta in an ...

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A photon is both a particle and a wave is utterly incorrect. A photon is the carrier of the electromagnetic interaction and does not appear in the description of quantum mechanics until you introduce quantum field theory. a particle doesn't have both speed and momentum defined values at the same time Maybe you mean position and momentum (velocity ...

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My issue here is it seems as though if his experiment were to be performed, it would violate known laws of physics. The picture and words in the section of the video you cited seem a little too vague to uniquely specify a specific experiment. But in the whole first 40 minutes of the video you see that all he is claiming is that we don't see departures ...

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In nonrelativistic quantum mechanics the wavefunction is defined on configuration space. So for $n$ particles there is a $3n$ dimensional configuration space. And the quantum wavefunction is a function from $\mathbb R^{3n}$ into the complex numbers (or into a joint spin state if you have spin). There could be regions where the wave is zero or very small, ...

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As a quantum theorist, this area of physics perfectly intersects my area of knowledge. A simple Google search can lead you to my favourite site for philosophical inquiry. The Many-Worlds Interpretation (MWI) of quantum mechanics holds that there are many worlds which exist in parallel at the same space and time as our own. The existence of the other ...

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I don't think that my terminology is suitable, because the term hidden realm carries the connotation of hidden variable theories, which is something else. I don't see them as very different. A hidden variable theory could take as the hidden variable the spinor or the wavefunction as a hidden variable. Many do. Events in the measurable realm ...

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A priori, they could have been different things. The Equivalence Principle - the hypothesis that they are actually the same - is a core input the General Relativity. To the extent that General Relativity is empirically validated, we have evidence that these really are the same. There's no complete theory of quantum gravity, so I think we'd have to say ...

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There are classical and quantum descriptions of the world. One of the differences of quantum description is paying attention to the process of measurement and how it affects the measured system. Description of measurements is an integral part of quantum description. Splitting this is into "realms" doesn't make much sense.

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It is wrong to describe the equipment as "faulty" . It is just different and when you carry out the experiment with the "different" equipment you will get a different answer.The scientific method requires that experiments be repeatable.So if you can repeat the experiment with the "faulty" equipment then you have just carried out a new experiment.

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No one thinks the wavefunction of nonrelativistic quantum mechanics is a wave in space and time. No one that wants to agree with observations that is. If someone is a realist about the wavefunction of nonrelativistic quantum mechanics then they start out by making a mathematical model by having the model include a wavefunction. Which when there are $n$ ...

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Imagine a simpler set up. You have a double slit and you purchase a super fancy which way device and out it next to the left slit. But you forget to remove the wrapper it came with. So it just goes off randomly at random times based on some thermal properties of say the wall current you plug it into. You might incorrectly think that almost all the ...

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Whether the MWI allows communication depends on what definition of communication you want to use. Communication in everyday life is something like this. I have information I want to send to you. I can arrange for you to have access to one copy while I have access to another. For example, you will be able to see this answer to your question on your computer ...

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It's my opinion that the reason is as follows. Time evolution is just an illusion, the future versions of you just exist out there. What we refer to as the time evolution according to the Schrödinger equation is not really a time evolution in the sense that things change. Nothing changes, we only ever have the same static eternal multiverse. All you are ...

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We don't need to worry about the whole universe here-- we can start with a single quantum coin flip in a sealed laboratory and take it from there. If you think you can consider a single particle in isolation then you fail to grasp the entire method by which separate worlds form in the MWI. It would be like it you tried to use the Copenhagen ...

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Your example is bad. The reason your example is wrong, as covered by Emilio Pisanty, is that measurement of your state simply results in getting some random $(n, f(n))$ pair, which is very easy to do classically; in the theory-framework of a non-deterministic Turing machine we would say that it certainly contains a "probabilistic state" which has to ...

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In principle there is nothing in the MWI which prevents communication between the different branches of the wavefunction. Indeed a (fairly controversial) paper was published in Foundations of Physics in 1997 with a proposal for an experiment to test this very possibility arXiv link. There are other proposals including several David Deutch which exploit the ...

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No. More explicitly, there's nothing particularly quantum about your scheme. This is easy to see because it fails the crucial test of replacing superpositions with mixed states. That means that you can replicate exactly the same protocol using the density matrix $$\rho=\frac{1}{2^m}\sum_x|x⟩⟨x|\otimes|f(x)⟩⟨f(x)|.$$ If you measure the output register in ...

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Let's say we have a quantum computer with two registers taking in $m$ and $n$ qubits respectively, with $m$, $n$ suitably large. Let $f:\{0,1\}^m \rightarrow \{0,1\}^n$ be a one-way function. According to wikipedia the existence of a one way function on the natural numbers would prove $P\neq NP$ which I believe means the Clay institute would give you a ...

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The Copenhagen interpretation (CI) doesn't say anything about the register. Or, rather, different versions of the CI may say different things about the register. The CI has a number of ingredients: (1) The CI rejects the idea that quantum mechanics (QM) is an accurate description of how the world works. (2) The CI claims that QM can nevertheless be used to ...

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In the Faraday pilot-wave fluid droplet dynamics, the fluid wave is meant as an analogy for the wavefunction. More specifically, the experiments are constructed as physical implementations analogous to the de Broglie-Bohm theory, where a particle with discrete coordinates is 'guided' by a pilot wave which follows the Schrödinger equation. To be a bit more ...

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In the oil droplet experiments that suggest de Broglie’s pilot wave theory might be accurate, what does the fluid surface correspond to? The three dimensional space that particle is moving through. But might I add that you shouldn't think of the particle as the oil droplet. Instead think of the particle as something more like a hurricane. The eye of the ...

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As a particle travels to a screen, it is traveling through 3-dimensional space. No, what happens is the configuration space of the system changes. This is essential for explaining interactions that destroy the interference. If your right slit deflected downwards and the your left slit deflected upwards then the two waves wouldn't overlap and hence when ...

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