# Tag Info

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The Schrodinger's cat thought experiment was an attempt by Schrodinger to show that cat cannot be alive and dead when it was not looked at. The thought experiment was appreciated by Einstein and Einstein said he appreciated Schrodinger for putting forth the experiment. This is where quantum and classical (the world we see around) physics mismatch. Some would ...

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The point of this thought experiment has been widely taken out of context and misused by new age science supporters. Schrodinger initially considered this experiment to show the RIDICULOUSNESS of the situation, not because it was physically what is happening. Additionally, anyone who says that there is a line between the quantum and classical regime is ...

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Note: There is a short summary at the bottom. This is actually also described in Nielsen&Chuang: You don't learn about general measurements, because they are completely equivalent to projective measurements + unitary time evolution + ancillary systems, all of which is described in your usual QM formalism. The Measurement Postulate Let's start from ...

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In the famous double-slit experiment using photons, you have a couple of configurations: Configuration A - 2 slits and 1 screen: After sending 1 photon at a time at the double slit, the photon hits the screen seemingly at random, but over time an interference pattern builds up. But each photon went through on its own, so there are no other photons for it ...

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Yes, you often see sources that say a parallax is found from measurements taken 6 months apart. That is rarely the case, and if you think about it, not all stars are visible in the night sky 6 months apart (from the same location on Earth). In fact a parallax measurement will consist of a series of measurements, possibly taken over more than 1 year. There ...

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You perform periodic measurements every 6 months. The measurements that are a year apart are only measuring the proper motion of the stars, this allows you to extract the parallax from the data.

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If you want to experimentally create a qubit, you need some actualization. One example is the z-component of the spin of a spin-1/2 particle such as an electron. There are two independent states which can be denoted $\left(\matrix{ 1 \\ 0}\right)$ and $\left(\matrix{ 0 \\ 1}\right)$ and each of which can be produced by orienting a stern-gerlach device in ...

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Is the probability $|c_1|^2 + \ldots + |c_k|^2$? Yes or no. It happens $\frac{|c_1|^2 + \ldots + |c_k|^2}{|c_1|^2 + \ldots + |c_N|^2}$ fraction of the time in the long run. (Assuming the states you listed were all normalized.) What state does the system jump into after this measurement? There is no experimental evidence of jumps or anything discontinuous. ...

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When someone says that spin measured about different axis can't both be known, they mean that whatever state you pick will have variability in at least one of the possible spin measurements you can do. So that is what you will get when measure the spin, you will get variable results. This happens even with entanglement with even just one particle. With ...

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As an experimental physicist, I go back to basics: Here is a double slit experiment a single photon at a time: The top panel shows dots from single photons coming in at the slits. The others the slow accumulation by which an interference pattern appears. That is what the experiment shows, dots like one would expect from single particles, ...

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As in John Rennie's answer we cannot describe the photon as being in a superposition of "going through different slits" states. But there is a sense wherein the answer to your question "Is a photon always in a state of superposition while traveling through space?" is almost always "yes". And the answer depends on a choice of co-ordinates. To answer the ...

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It basically boils down to this. Looking at a flying electron through a camera, there is no interference. Nothing special. But not trying to find which slit it went through and gradually observing the electrons to hit the detector there is interference pattern. In other words, when trying to find which slit the electron went through, wave function collapses ...

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Things are amazing for as long as you do not (or refuse to) understand them! What happens is that, counterintuitively, everything around us is waves (matter or de Broglie waves). Hence they naturally interfere, producing for example the diffraction patterns behind a double slit (or indeed even a single slit). Waves naturally and unsurprisingly obey the ...

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If we take two slits large enough for bowling balls and with a much smaller than the ball separation , and a pile of bowling balls and design a catapult throwing the balls at the slits parallel to the ground within the window covering the two slits, what will happen? 1) some balls will pass through one of the slits without touching, straight ahead 2)some ...

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Further to Anna V's answer, in the case of an electron there is an important physical meaning to the "lack" measurability of the phase of the electron's wavefunction. This is because the electron is coupled to the electromagnetic field. And, if one models this by the Minimal Coupling between the electron and the electromagnetic field, one gets the ...

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What does measurable mean ? It means that one can do an experiment and get a value for a+ib , the complex number. A complex number to be measurable one should be able to measure a value at the same time for a and b and put a point on the complex plane. This means two independent variables, a and b can be measured and a point defined. In quantum mechanics ...

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Ψ is supposedly a probability density amplitude. ΨΨ* is the probability density which in theory can be measured. For example in electron diffraction through a crystal a statistical measure of the electrons in, divided into the electrons out in a small region divided by the volume would allow ΨΨ* to be approximately measured. Phase information is lost when ...

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I am not supposed to place an answer here, as I am no more active in this site: however, a comment doesn't offer enough place. So, you ask: 1) "spin is a property of the wave function, and not of the particle?" Please pay attention to the following differences between the standard quantum theory (SQT) and the Bohmian interpretation (BI): SQT ...

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Do interpretations of quantum mechanics have physical meaning? Yes and no. There's not much physical meaning behind the Copenhagen Interpretation, and even less behind the MWI. But these are not the only way to skin Schrödinger's cat. Which I'm sure you know, was proposed to by Erwin to show how ridiculous the Copenhagen Interpretation was, but has since ...

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If interpretations actually had different physical consequences, we might go about calling them different 'theories' instead. For example, one might say that the classical Newtonian model of gravity comes from many non-interfering (straight line) threads of variable length, maybe with complex infinitesimal modern art on them, (in fact, undetectable in any ...

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Different interpretations may have different physical meanings. For the most part they probably act to "translate" the reality into something intuitive for the person, but some may make unique predictions that just aren't tested yet and we cannot yet know if the interpretation is accurate.

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