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2 votes

Can we use entangled particles to find out what is going on inside a black hole?

This is a version on steroids of the famous Einstein–Podolsky–Rosen Paradox. In General Relativity, to get out of a black hole requires you to move faster than light, so your question can essentially ...
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1 vote

FTL signaling by direction?

Yes, that would be FTL communication, but no it is not possible to do. To convince yourself, ask yourself: If person A measures first, which measurements can person B do, to tell which axis A measured ...
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1 vote

What's wrong with my argument about entanglement entropy in QFT being time-independent?

You are implicitly making a very strong assumption in your argument. Given $$ H=H_A+H_{\bar A}, $$ $$ e^{\pm iHt}=e^{\pm i(H_A+H_{\bar A})~t} $$ is true, but your next step $$ e^{\pm i(H_A+H_{\bar A})~...
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0 votes

Role of entanglement in quantum computing

David Deutch has argued that quantum computers work by running the computation in lots of parallel universes simultaneously, arranging them so that the wrong answers all get cancelled out. If you ...
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2 votes

Role of entanglement in quantum computing

It's not true that entanglement is what makes quantum computers faster. The Gottesman-Knill theorem showed that many quantum algorithms that rely on entanglement can be efficiently implemented ...
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2 votes
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How does measurement work in this Multi qbit entangled system?

Measurement in the $|+\rangle = \frac{1}{\sqrt{2}}(|0\rangle + |1\rangle)$ and $|-\rangle = \frac{1}{\sqrt{2}}(|0\rangle - |1\rangle)$ can be expressed in terms of a Von-Neumann measurement. i.e, ...
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1 vote

Can you create a pair of entangled particles with asymmetric probabilities of quantum states?

I assume that "particle in state $A$" and "particle in state $B$" are typos for "particle $A$" and "particle $B$". Is it possible to create an entangled pair of ...
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0 votes

Can you create a pair of entangled particles with asymmetric probabilities of quantum states?

send the particle with state A left and the particle with state B right By definition of "quantum" the states are controlled by quantum probability ( $Ψ^*Ψ$) So the space state of ...
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2 votes
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Computation of two-site entanglement entropy of the critical transverse-field Ising chain

The problem arises because of an incorrect expression for $\langle\sigma_0^z\sigma_1^z\rangle$. The correct expression is $$ \langle\sigma_0^z\sigma_1^z\rangle = \langle\sigma_0^z\rangle \langle\...
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2 votes

Where does the black hole firewall energy come from?

The firewall is a thought experiment stressing an incompatibility between previous agreed pictures, few actually consider it an actual physical entity. The common belief is that some of the ...
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-1 votes

Where does the black hole firewall energy come from?

No one really has a good answer to this because the firewall is only theortical with no expieimental evidence to back it up. (It is a seperate question if evidence even could exist in the first place ...
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3 votes
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Entanglement entropy of the infinite transverse field Ising chain at the critical point

These few-site entropies tend to converge fairly fast with finite size, because they ultimately depend on very local physics. If you switch to DMRG you should easily see the values converge fully. You ...
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0 votes

What Class of Interactions, excluding spontaneous pair creation, Entangle two particles

The confusion here seems to be a mix of classical and quantum terminology. You discuss the most famous multi-particle system with no entanglement (neglecting the Schwinger effect), which is a pair of ...
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1 vote

Mixed separable state with a continous probability distribution

The key point here is Caratheodory's theorem: If a state can be written as a convex combination of tensor products of density matrices, such as your integral, then it can also be expressed as a convex ...
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1 vote

Questions on Bell's theorem and Disproving the hidden variable theory

I'm going to update part your RSA token analogy to reflect the experimentally observed behavior of entangled particles. Hopefully this helps demonstrate why the hidden-variables theory doesn't work. ...
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  • 121
0 votes
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How does the many-worlds interpretation solve spooky action at a distance?

In the Everett Interpretation (often called the Many Worlds Interpretation), when an 'observer' system interacts with an 'observed' system in a superposition of states, the result is that the observer ...
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1 vote
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Quantum extremal surface and black hole evaporation inquiry

First of all you are looking at the calculation of the generalised entropy of the black hole radiation inside the cutoff region. The paper then goes to do the calculation of the region beyond the ...
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  • 4,300
1 vote
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Mixed separable state with a continous probability distribution

Yes, provided that $$ \int p(a)\ \text{d}a = 1 $$ the mixed state defined in terms of such an integral represents a valid separable state.
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1 vote

Understanding Entanglement basis change in a practical sense

You've made this harder than it needs to be by choosing $R$ and $L$ with different lengths. You can always replace a state vector with a parallel vector of the same length without affecting any ...
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1 vote

Representation of an entangled state

I think your confusion stems from what is the system and what is the state. The system is the measurement apparatus, which sometimes leaves the state of the particles unchanged if it happens to be ...
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2 votes
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What is meant by the term "elements of physical reality" used by EPR paper?

The original article by Einstein, Podolsky and Rosen includes the following paragraph: The elements of the physical reality cannot be determined by a priori philosophical considerations, but must be ...
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1 vote

What is meant by the term "elements of physical reality" used by EPR paper?

Every particle has “elements of physical reality”. We couldn’t detect them if they didn’t. These elements, also known as variables could be as simple as mass, velocity, direction, angular momentum/...
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0 votes

2 qubit entanglement in a QC

Generally speaking, the practical limitations of quantum computing are in the form of noise, and quantum decoherence, both of which occur due to interaction with the environment. Noise in quantum ...
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3 votes

What is meant by the term "elements of physical reality" used by EPR paper?

The widely accepted view of nature of reality is that of copenhagen interpretation(please correct me if I am wrong!) I am not sure whether it is "widely accepted" today. Bohr and company ...
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Intuition/Motivation behind mixed states

It is better, I'd suggest and given this, to not think of vectors in the Hilbert space as "states", but as a sort of "raw material" for building states. In fact, there are ...
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1 vote

Intuition/Motivation behind mixed states

Mixed states allow you to describe classical uncertainty, in addition to quantum uncertainty. Quantum uncertainty, as descriped by superposition of states, is familiar from an introductory quantum ...
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