All Questions
33 questions
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Wave function collapse, EPR paradox and information transfer
For a classical formulation of the EPR paradox, two particles are produced, with total momentum zero and separated by a long distance. So say we measure the momentum of one particle first, and measure ...
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Will the electron interference remain if the photon scattering method doesn't include a photo-detector? Is it an example of quantum entanglement?
It is actually not a question. I am giving a chain of arguments here , I believe at some point I made a mistake. I want the mistake to be pointed out.
/1. The probability of an event in an ideal ...
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2
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212
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If measurement causes entanglement with the observer, is any further measurement possible?
When an observer measures a system, the systems wavefunction collapses and they become entangled. Does this mean that any further measurement by the observer on the system is impossible, as the system ...
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1
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Trouble understanding the math of the preferred basis problem
I've been trying to understand the preferred-basis problem in QM, specifally in the Everettian intepretation.
To quote an answer to another question which discusses this:
In my opinion, the situation ...
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2
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Have objective collapse theories been ruled out by recent experiments?
Have objective collapse theories been ruled out by recent experiments, such as the entanglement of macroscopic objects? (vibrating drumheads)
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1
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3k
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How does the notion of weak measurement resolve Hardy's paradox?
How the notion of weak measurement resolves Hardy's paradox?
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Are there known paradoxes regarding a detector that was, before use, entangled with a particle it detects?
Is it possible to design a system where a detector is entangled with the particle state it detects (before it is detected), and to create a paradox from this?
Upon observance of a state by the ...
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5
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2
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594
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Decoherence: faster than light?
The answer to this question suggest that one can solve the measurement problem by decoherence. If I understand it correctly the decoherence appears when the quantum state interacts with the ...
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2
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Current quantum theory does not offer a dynamical mechanism to account for energy transfer in position-measurement, WHY?
In Quantum Mechanics (vol. 1) by Tannoudji et al., there are two pages discussing "perturbation created by a position measurement" (p.278-279). They consider a particle in an infinitely deep potential ...
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1
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What initiates quantum entanglement?
In a previous question, I asked about the measurement problem in quantum mechanics. The sense I got is that the best interpretation we have is the many worlds interpretation, and one of the answers ...
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1
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Potential FTL Implications of quantum "weak measurement"?
Physics noob here. I can't find a good answer to this thought experiment that is consistent with general relativity and It's really bothering me. I'm probably missing something huge but just can't ...
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Can two entangled electrons can get disentagled in Nature, withous us making a measurement?
Imagine we have two free, entangled [by their spins, which are in this case non-separable, while $x$ (or $p$) electrons are clearly separable]. In an experimental setup, we can measure (and observe) ...
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2
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Why do lasers in open air produce 2-slit interference patterns? [closed]
I saw this answer:
Is quantum entanglement functionally equivalent to a measurement?.
I had follow up questions that seem to have been addressed. Here are just a few similar topics:
Why does ...
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15
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6
answers
3k
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Entanglement, real or just math? [duplicate]
In quantum entanglement when something acts on one particle the other one reacts also, just in reverse (more or less). From what I've read though, anything acting on either particle will collapse the ...
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What processes cause the collapse of a wavefunction and break entanglement?
This question states that measuring the spin of an entangled particle causes the collapse of the wavefunction and thus the entanglement is broken.
Then this question states that we don't know what ...
CommunityBot
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2
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Can we determine whether or not a particle is entangled?
Suppose Shaniqua and Tyrone have four pairs, a, b, c, and d, of entangled particles. They take their particles and go very far apart. If Tyrone can determine whether or not a particle is still ...
- 21.4k
5
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2
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278
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Prepared states and quantum entanglement [duplicate]
Imagine two entangled quantum particles in the singlet state, one held by Alice and the other by Bob. Alice and Bob are both widely separated. Bob measures his spin in some axis and finds it to be ...
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3
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Uncertainty Principle - measuring momentum on one entangled particle, position on the other
If two entangled particles are sent far apart and then at exactly the same time the position of one, and the momentum of the other, is measured, won't this mean that, because the corresponding values ...
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1
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Quantum entanglement and affecting the particles [duplicate]
I am trying to grasp some aspects of the quantum entanglement, but the existing resources (including some of the links here) seem a bit confusing. I am trying to find an answer to the following ...
CommunityBot
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Implications of weak measurement on entanglement
What are the implications of weak-measurement on entangled particles, and how does that resolve the problem of non-superluminal quantum "communication"? If I understand correctly, entangled particles ...
CommunityBot
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2
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1
answer
219
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Quantum non-locality with commuting measurements?
We consider the Bell scenario, in which Alice and Bob share an entangled pure quantum state $\mid \Psi \rangle_{AB}$. Alice gets an input in the set $\{1,2\ldots X\}$ and Bob gets an input in the set ...
- 181k
0
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1
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Quantum Measurement of Entangled Time-Varying Systems
Suppose System A has a dynamic, continuous variable $O_A(t)$, which we wish to measure via a quantum probe. Assume system A has a self-Hmiltonian, $H_{SA}$ so that the evolving wave function of ...
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1
answer
875
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How to understand the measurement on entangled state in the following cases? [closed]
Assuming an EPR pair AB, event MA is a measurement on A.
My questions are:
(1) At MB and MB' (depending on where B is located), if we try to describe the state of B (but not measure B yet), what's ...
- 213k
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5
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Is quantum entanglement functionally equivalent to a measurement?
I saw the following talk the other day: http://www.youtube.com/watch?v=dEaecUuEqfc&feature=share
In it, Dr. Ron Garret posits that entanglement isn't really that "special" of a property. He ...
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2
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115
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In quantum mechanics does the truth/accuracy of a measurement really matter?
Once John Wheeler said "the past has no meaning or existence unless it exist as a record in the present". So, in a experiment of delayed choice entanglement swapping, if we used a faulty detector to ...
- 213k
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2
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420
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Quantum Entanglement - How To Interpret [duplicate]
I have thought about quantum entanglement for some time, and I still don't quite understand the reasoning behind the conclusion that entangled particles somehow can communicate their state to each ...
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3
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1
answer
439
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Entanglement and the uncertainty principle
Suppose you have two maximally entangled particles. You measure the spin about the x axis of the first and the spin about the y axis of the second. But both spins cannot be known simultaneously, so ...
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4
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6
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915
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Explanation for the EPR-like paradox
I am trying to understand the process of Quantum Entanglement for use in Quantum computers.
The problem I have is this:
Suppose some nuclear process emits an electron-positron pair. Now after ...
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2
answers
3k
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Entanglement and simultaneity
According to the special theory of relativity, distant simultaneity depends on the observer's reference frame.
And, according to the quantum theory, in the case of two entangled particles, a measure ...
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4
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How is it possible that quantum phenomenons (e.g. superposition) are possible when all quantum particles are being constantly observed?
I don't understand how quantum mechanics (and therefore also quantum computers) can work given that while we work with quantum states, particles that this quantum state consist of cannot be observed, ...
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1
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What happens to entangled particles when momentum is measured?
In Wikipedia it is mentioned that position and momentum can be entangled as well as spin and polarization etc. I assume etc. is charge etc.
I understand how if you measure spin up on one of a pair you ...
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1
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Quantum Entanglement - Measuring Twice
In the answer here and on the wiki article and many other articles it is mentioned that if one of 2 entangled particles is measured their state collapses according to the Copenhagen interpretation.
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4
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Is a macroscopic pair where I observe one of them quantum entanglement?
Of what little I know/understand about quantum entanglement can somebody confirm if the following experiment is a good analogy to quantum entanglement of pair of particles? PS: please don't laugh as ...
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