Questions tagged [quantum-entanglement]
Quantum entanglement is the mechanism by which quantum correlations between two sub-systems survive even after being physically separated from an interaction region. The correlations could in principle survive without neither time nor space constraint.
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Vacuum flucutuations = local entanglement between quantum fields?
I'm puzzled by this statement by Dieter Zeh: "Various types of quantum fluctuations (in particular vacuum fluctuations, often visualized in terms of 'virtual particles') are used to describe ...
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Can a density matrix represent an eigenstate of an observable? [closed]
What is an observable for which the state represented by the following density matrix is an eigenstate?
$\rho_\alpha = \frac{1}{2}(|+1\rangle\langle+1| + |-1\rangle\langle-1|)$?
Is it correct to think ...
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Are states partially ordered in the same way via entanglement and Bell violations?
Recall what a partially ordered set is.
Let $E(\rho)$ be an entanglement measure. Let $B(\rho) \leq 0$ be a Bell inequality. Define the Bell violation measure with respect to $B$ as
$$\tilde{B}(\rho) =...
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Why can we not experimentally evaluate the expectation value of the CHSH operator after simplifying its expression to check entanglement?
We have the observable corresponding to the CHSH inequality given by,
\begin{align}
\mathcal{\hat{S}} &= \hat{Z}_1 \left(\frac{1}{\sqrt{2}} (-\hat{Z}_2 - \hat{X}_2)\right) + \hat{X}_1 \left(\frac{...
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Where to find the Expectation Values of Aspect's and Clauser Experiments [duplicate]
Alain Aspect and John Clauser won the Nobel Prize in Physics for their epxeriments on quantum entanglement. Does anyone know where to find the raw data or at least published calculated expectation ...
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Bell's inequality in Claude Cohen-Tannoudji's Quantum Mechanics Volume III
Claude Cohen-Tannoudji et al, Quantum Mechanics Volume III, 2020 edition, Chapter XXI.F-3-b.$\alpha$ (F-7) on p.2210 states
$$\big\langle\hat A(a)\hat B(b) \big\rangle={\cal P_{++}+P_{--}-P_{+-}-P_{-+}...
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Example of a classical correlation and a quantum correlation
I'm trying to understand the fundamental differences between classical and quantum correlations through examples of a quantum entangled state and a classically correlated state.
I know that this is an ...
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When is a state entangled?
I have read from What's the difference between an entangled state, a superposed state and a cat state? that an entangled state is one that cannot be expressed as product state. Suppose we have the ...
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What is a physical example of entanglement occurring naturally?
What is a physical example of entanglement occurring naturally? I am looking for an instance that I would see in nature outside the lab. I am looking for this example to be concrete and physical.
I ...
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Is it possible that a macroscopic object tends to a separable state without the need for objective collapse?
For a multi-particle system, superposition is in some sense equivalent to entanglement; with the Dirac field being treated as classical under second quantization, for example, we could at least argue ...
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Understanding entanglement [duplicate]
I’m probably missing something obvious. I'm new to physics, so please bear with me. Imagine flipping a perfect coin in a vacuum. The moment we through it up it splits exactly in half, with both halves ...
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Whats wrong with concept of "faster than light" information transfer device? (not about technical implementation, just about theory) [closed]
Yesterday, while lying in bed, an idea came to me, and I don’t understand why it won’t work?
Setup:
1.1) Two infinite stores of entangled pairs of photons, each connected to a double-slit device.
1.2)...
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Importance of Environment in System-Observer Entanglement and Decoherence
It has been stated in places such as Sean Carroll's talks that including the environment in our description of a quantum measurement process is important in understanding why we do not "feel like&...
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Transmitting Data faster than the speed of light using entangled particles [duplicate]
If we have a pair of super-asymmetrical entangled particles, and move them a light year away so that they retain their quantum entanglement, and we set a clockwise spin (or vertical polarization) as 0 ...
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Why can quantum entanglement not use temporal encoding to transmit information? [closed]
It's common knowledge that quantum entanglement can't be used to transmit information; however, I'm struggling to understand why an encoding based on time intervals in which measurements are made ...
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