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19

First, a historical subtlety: Schrödinger has actually stolen the idea of the cat from Einstein. Second, both men – Einstein and Schrödinger – used the thought experiment to "explain" a point that was wrong. They thought it was absurd for quantum mechanics to say that the state $a|{\rm alive}\rangle+b|{\rm dead}\rangle$ was possible in Nature (it was ...


8

What's wrong with my reasoning? Nothing! In fact you have more or less described decoherence. The idea is that any system inevitably interacts with its environment, and the more degrees of freedom the system has, i.e. the more complex it is, the faster it will interact with the rest of the universe and the superposed states will decohere.


7

The thought experiment aimed at illustrating one concept, and questioning the validity of such concept: 1/ The concept: in quantum mechanics, before an observation is made (note the cat is in a closed box, and nobody can see what is going on in the box), a system is not in a defined state, but only has a certain probability to be in any state - here the ...


4

You don't explicitly say so, but you're assuming the Copenhagen interpretation (CI) rather than the many-worlds interpretation (MWI). Your analysis is a perfectly good example of why the CI doesn't fundamentally make much sense. The CI treats measurement as a process that's different from other processes, even though measurement is a physical interaction ...


3

You're right that this experiment isn't really a realistic one. In fact, it's difficult to imagine how we could even tell whether a given box were such a perfectly isolating box. However, if we put aside the (somewhat important) question of empirically determining whether we actually obtained a cat in a superposition of life and death, we can try to imagine ...


3

The expression in the picture contains kets only. Kets represent states of a system. In this case, the "alive" state is the first one and the "dead" state the second. The numerical factors are there for normalisation. It is assumed both states are equally likely, so they have the same numerical factor. If we call the expression in the picture ...


2

In Schrodinger’s cat experiment there is a mixture of a macroscopic object, the cat, and a quantum mechanical object, the radioactive atom, which if decayed it would activate a hammer to break the flask, with the poisonous gas in it, and therefore killing the cat. This description is very straight forward and not very hard to understand: the cat in the box ...


2

Ket(s) and Bra(s) represent state of a system. The simplest interpretation is to see kets and states as (complex) vectors. In your case, the state could be described by the vector : $$\vec S = \frac{1}{\sqrt{2}} \vec{alive} + \frac{1}{\sqrt{2}} \vec{dead}$$ Here, $\vec{alive}$ and $\vec{dead}$ are a basis for the states, so they are orthogonal vectors : ...


2

This is a thought-provoking question, but... the concept of observer is only important if one takes the Copenhagen interpretation. So let us stick to that for the purpose of answering the OP. The cat cannot be an observer of itself. In the logic of the Copenhagen set-up, there is a quantum mechanical object being observed, a classical measurement ...


2

The equation (5.36) in the (newest version) of the paper is: $$ρ_S (x, x′ , t) = ρ_S (x, x′ , 0) e^{ −γt\left(\frac{x−x'}{\lambda_T}\right)^2} \tag{1}$$ where $\rho_S$ should be the off-diagonal term in the density operator, $\gamma$ the relaxation coefficient and $\lambda_T=\frac{\hbar}{\sqrt{2Mk_BT}}$ is the thermal de Broglie wavelength of the system. ...


2

Your question effectively reduces to that of where you place the Heisenberg cut in an idealized model of the experiment. That's not different from the issues that are already probed by the original thought experiment and the Wigner's friend variant. It's implicit in the quantum formalism that (unless one introduces POVMs) one models experiments using ...


1

See Is Schrödinger’s cat misleading? And what would happen if Planck constant is bigger?. This isn't an exact duplicate, but it explains why we do believe the cat can be in a superposition of states, but the superposition only lasts a very very short time before it decoheres. The decoherence has nothing to do with consciousness, simply the number of ...


1

There was a lot of disclaimer that was implied. For one, a "box" in physics is much better at containing things than the cardboard boxes you see containing cats on the internet. The box here is understood to not allow any information to pass through its walls except where and when we specify. That is, there is no environmental contamination to decohere ...


1

I have always disliked this thought experiment because, even though it was proposed as an amplifier of quantum mechanical effects, it is really nothing more than a game on probability, and one can get random probabilities by many classical means. Toss a coin, heads cat alive tails cat dead. The concept of both alive and dead is ridiculous in the ...


1

The easy part is the numerical coefficients which are there so the state is normalized, which means $\langle \psi | \psi \rangle=1$. The easier part is what's written in the kets, one of them illustrates the state of a dead cat and the other a living one. The point is, due to the canonical form of quantum mechanics, before doing a measurement the cat's ...


1

For the same reason that macroscopic objects do not display quantum mechanical behavior, except in very special setups, as in superconductivity etc. Macroscopic systems in general, due to Avogadro's number which is something like 10^23 molecules per mole, cannot be described by one quantum mechanical wave function .They are an incoherent superposition of ...


1

There is also another possible solution to this problem which fits perfectly well, but its a strange solution that turns everything outside in. In the June number of Scientific American there was an article about Quantum Bayesianism where the wave equation of all objects is placed in the mind of the observer. This explains why the act of observing a photon ...


1

The experiment is intended to highlight the problem of quantum superposition applied to macroscopic objects. It's not inconceivable that a radioactive nucleus can be in a superposition of states. When you interact the nucleus with the detector, hammer and glass of poison, the wavefunction that describes these items become entangled with the wavefunction of ...


1

There are two states (in QM with ket's $\left|\phantom{H}\right>$ we mark possible states) of the Schrödinger's cat. 1st state means (the one on the left) the cat is alive and 2nd state (the one on the right) means it is dead. We could write this down like this: $$\underbrace{\frac{1}{\sqrt{2}}}_{\llap{\text{amplitude for first state}}} ...


1

Decoherence happens because in a macroscopic system you are not able to create a small isolated system. In practice you are deal with statistical mixture and not pure state. There's a good description on Wikipedia.


1

Schrödinger's cat is a thought experiment, sometimes described as a paradox. The scenario presents a cat that may be both alive and dead, depending on an earlier random event. Although the original "experiment" was imaginary, similar principles have been researched and used in practical applications. The thought experiment is also often featured in ...



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