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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Question about entanglement [closed]
(There are a lot of questions about entanglement shown in the Similar Questions box. If there's already something about what I'm about to ask, please refer me there.)
Suppose the particle paths are ...
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Correlation between Entangled Particles in a Chain Sequence [closed]
Suppose we have two entangled particles, A and B. If we measure particle A and then subsequently entangle particle B with a third particle, C, would the state of particle A influence the combined ...
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For tetrapartite state, and another way of decomposition, is the Schmidt basis close to separable? [duplicate]
Consider two tetrapartite quantum states $|\phi\rangle^{AA^\prime BB^\prime}$ and $|\psi_1\rangle^{AA^\prime}|\psi_2\rangle^{BB^\prime}$ in a finite dimentional Hilbert space $\mathcal{H}^A\otimes\...
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Wigner function for a Non-Gaussian Continuous Variable Bound entangled state [closed]
Is it possible to write a wigner function for the state described below?
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How can we figure out what fraction of pure states in a Hilbert space are entangled? [duplicate]
The full Hilbert space of a quantum system will generally contain entangled states, and thus when entanglement is lost through decoherence, parts of Hilbert space become inaccessible. Is there a ...
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Is there a relation between some kind of distance and the Schmidt basis?
Consider two bipartite quantum states $|\phi\rangle^{AB}$ and $|\psi\rangle^{AB}$ (in a finite dimensional Hilbert space $\mathcal H_A\otimes \mathcal H_B$), such that
$$\| |\phi\rangle\langle\phi|^{...
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Does no-communication theorem imply monogamy of entanglement? [closed]
This is the statement I think must be true: "It is impossible to have a non-separable multipartite quantum entanglement such that all of its components collapse to a consistent eigenstate upon ...
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Scattering of entangled states
Recently, I became interested in scattering processes which involve an initial and final state that consists of entangled states (lets say $\left|e^{-}\right\rangle \times\left|e^{+}\right\rangle $ or ...
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How to calculate mean in phase space for entangled Gaussian state after high losses and a strong thermal background channel? [closed]
I would like to ask how to calculate the mean in phase space for entangled Gaussian state for both the hypothesis (H0 and H1)?
E.g. from https://arxiv.org/abs/0810.0534v1 we have a coherent Gaussian ...
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How is a delocalised state realised and what is its wavefunction?
Gravitationally induced entanglement experiments aim at studying the quantum nature of gravity trough the interaction of a delocalised particle state with another system. The various papers on the ...
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I have a confusion regarding Entanglement [duplicate]
What I have learned about Entanglement during my Quantum Mechanics Major Course that when two particles are entangled or their state is correlated somehow, if we do a measurement on one of them, we ...
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Spontaneous Parametric Down Conversion (SPDC): why the asymmetric Bell state?
I'm reading various introductions to SPDC, and they all seem to take the state of the entangled photons to be the Bell state that is asymmetric under exchange:
$$\Big( \left| H\right>_1\left| V\...
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Relative "volume" of entangled vs product states [duplicate]
A system containing $n$ qubits is described by a $2^n-$dimensional Hilbert space. Some of these states can be decomposed as product states, but not all of them. The remaining ones are called entangled ...
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In observing EPR phenomenon, which direction is opposite to the other?
I have a question about the EPR phenomenon of the quantum-mechanics.
When you observe the EPR phenomenon, you separate two spins in the singlet state. Then, you and your fellow independently observe ...
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Why quantum entanglement for a non-local object needs explanation?
I am a little confused about the usual explanations about quantum entanglement.
In the Schrödinger picture, the state vector evolves in time.
In the Heisenberg picture, the state vector does not ...
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Communication via entanglement [duplicate]
For years now i have in my haed a thought experiment for information exchange via quantum entanglement. And i am aware that something must be wrong with it but i can't figure out what it is.
The ...
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What are the implications of entanglement swapping for the Pusey-Barrett-Rudolph (PBR) theorem?
The derivation of the PBR theorem makes an assumption that "systems that are prepared independently have independent physical states". However, it is known that it is possible to entangle ...
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Factorization of density matrices
I'm currently reading through the following document about quantum noise and open quantum systems: https://courses.cs.washington.edu/courses/cse599d/06wi/lecturenotes13.pdf. On page 6 of the document, ...
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Instantaneous transmission of data across arbitrary distances via quantum entanglement [duplicate]
As a forward, I'm no a physicist or a student of it. In fact I'm pretty ordinary. So if I mischarecterize some concepts, bear with me.
So I was reading up on some of the new technologies and then I ...
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Delayed choice quantum eraser setup with no beam splitter?
I know this question has probably been discussed many times before. But, I need a clear answer about this setup, in case there is no beam splitter.
What is going to happen in this situation? My ...
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Entanglement entropy as the source of Bekenstein-Hawking entropy
I think I'm missing something about interpreting a black hole's entanglement entropy as the source of it's Bekenstein-Hawking entropy, and I can't find any literature on it.
So, we know that our ...
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Faster than light communication by entangled photons [duplicate]
Faster than light communication is not possible. If I measure the polarization of an entangled photon and it turns out to be right circularly polarized. In that instant, dont I know that someone ...
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Does entanglement in a quantum physics experiment automatically cancel the interference?
Background: I'm currently doing self-study of quantum physics by following university level quantum physics lectures on YouTube (e.g. the YouTube MIT 8.04 Quantum Physics I, Spring 2013 or Stanford ...
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Are there non-trivial two-party stabilizers in bipartite entanglement for product states?
In this recent paper where the authors discuss finite classification of entanglement types, on pg. 29 in appendix A, it is claimed that in bipartite entanglement for product state $|00\rangle$ there ...
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Topological band crossing and central charge
Conventionally for a 1D topological insulator, SSH model for example, the low energy assumes a linear dispersion i.e. Dirac cone at a topological phase transition point, thus obeys the massless Dirac ...
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How exactly do triple photon entanglements behave? [closed]
I recently learnt that more than two photons can be entangled.
Are all the three photons are expected to have the same polarized angle due to entanglement?
Does measuring one of the three photons ...
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Can entanglement cause a chain reaction at distance after measure one particle? [duplicate]
if we have two electrons with their spins entangled like this:
And if we measure the spin on the left electron, then right electron spin also change like this:
So, my question is, do this spin ...
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MWI and splitting before entanglement
Recently I saw a conversation between Sean Carroll and Slavoj Zizek concerning the MWI.
One of the questions that drove Slavoj concerned with this question of Ontology vs. Epistemology, as the way ...
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Is there any minimalistic version of superdeterminism theory?
Superdeterminism is one wild conjecture which is an alternative to the standard quantum mechanical interpretation and preserves local realism
Superdeterminism seems to be too much of a stretch. If ...
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Do entangled coherent states violates Heisenberg limit?
In the ideal quantum information version of metrology, a maximally entangled
state is viewed as the best resource for quantum metrology. The optimal phase uncertainty of the NOON state reaches to the ...
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Experimental Demonstration of Entanglement?
In many papers about entangled sources, they use an experimental setup like this one to demonstrate their entanglement:
The setup involves measuring coincidences at the detectors at various angles of ...
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How non-degenerate photon pair can be entangled?
papers like below describe https://arxiv.org/abs/1305.0986 "A Flexible Source of Non-Degenerate Entangled Photons Based on a Two-Crystal Sagnac Interferometer"
I, somehow, thought that ...
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Is the possible Bell's test loophole of entangled particles communicating at a non instantaneous but FTL speed addressed and eliminated? [closed]
TLDR:
There seems to be a loophole in Bell's test that is not addressed or eliminated before we can successfully conclude that it proves that the Universe is unreal and non local. The entangled ...
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Can I perform entanglement swapping on an entangled pair with another 2 pairs simultaneously?
Suppose that I have 3 entangled pairs (a1, a2), (b1, b2), (c1, c2). Can I perform entanglement swapping on (a2, b1) and (b2, c1) simultaneously to get a new entanglement pair (a1, c2)?
The question is ...
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What information is gained when just one single half of an entangled photon pair is detected, following its transmission through a polarizer?
My admittedly limited understanding of QM is that it is a matter of probabilities whether or not a photon is (re)transmitted through a polarising filter and that these are a function of the relative ...
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How can we be sure Bell's theorem disproves local realism when we are not sure whether the measuring apparatus is in some form of entanglement or not? [duplicate]
Bell's therorem seems to disprove localism because measuring, let's say spin of an entangled electron, seem to communicate the measurement to it's another pair instantaneously.
But isn't another thing ...
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Local Gravitational Time Dilation Effects on Entangled Particles
If Alice is located just beyond the event horizon of a black hole, and Bob is at some other point in space with de minimis gravitiational effect, what, if any, effect would it have on the "spooky ...
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Entanglement entropy in states with particle content
I am studying entanglement and its measurements in the context of a lattice model of the Dirac theory. The idea is that one has two bands, symmetric with respect to $E=0$, and the groundstate is ...
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When does multi-particle entanglement break? [closed]
Let's say we entangle four electrons based on their spin.
Now, let's say we measure the spin of electron A along the z-axis (up/down), and we observe a spin of 'up'. My understanding is that this ...
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Can you provide an example quantum system that violates Bell's inequality? [closed]
I am self-learning QM. I am reading this paper about Bell's theorem https://arxiv.org/pdf/1212.5214.pdf and having difficult to understand the quantum system example in the paper that violates Bell's ...
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How can time-evolution lead a Nèel-ordered state to an entangled state?
I am working with a system governed by the Following Hamiltonian:
H = $\sum_{i<j} J_{ij}(\sigma_i^+ \sigma_j^- + \sigma_i^- \sigma_j^+) + B\sum_j\sigma_j^z$
The Time evolution is:
$|\psi(t)\rangle =...
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Entanglement in the Born-Oppenheimer approximation
Consider a scenario where we aim to model an atom as a system consisting of two components: the nucleus and the valence electron.
In this approach, we simulate the behavior of the electron within the ...
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Entanglement measure for a continuous bipartite system
Consider a cavity-spin system and assume we want to quantify the correlation between them. The cavity system can be described using a bosonic mode whereas the spin system requires 2 bosons to describe ...
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Quantum Information Theory: How do I perform entanglement quantification calculations using the Quantum Heisenberg model?
I have been reading Quantum Computation and Quantum Information (10th edition) by Nielsen and Chuang and I am interested in calculating the level of entanglement (with entropy or some other measure I ...
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How efficient are coincidence counting techniques?
Obviously there is a limitation as to how well experimental configurations that depend on coincidence counting can efficiently remove the noise present at any given experiment. This leads me to ...
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Confusion about the tensor product structure of a multi-fermion Hilbert space
I often see people study entanglement in fermionic systems. The setup is often like this. Suppose we have a 1d lattice of $2L $ sites, which is divided into a left part and a right part, each with $L ...
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Macroscopic Example of a Quantum Entanglement Thought Experiment [duplicate]
Being a layman in the sense that I enjoy reading about physics concepts, but lack the deeper mathematical understanding, I've been trying to wrap my mind around the concept of quantum entanglement and ...
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Can quantum interference be detected in entangled pairs?
If I had a pair of entangled particles that were both in superposition, and I put one of them through a interference experiment, such as the double slit experiment, would I see an absence of ...
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Superposition of Page times - is the Hawking radiation maximally mixed?
Suppose we have a black hole of mass $M$ at time $t_0$. The black hole has already been radiating Hawking radiation for some time. If no further mass is added to the black hole, suppose over half of ...
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Why is the GHZ state not rotationally symmetric?
Consider three spin-1/2 systems. Prepare them in the GHZ state:
$|GHZ\rangle=\frac{|+z,+z,+z\rangle + |-z,-z,-z\rangle}{\sqrt{2}}$
Suppose one measures spin along the X axis for all three systems. If ...
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