All Questions
Tagged with quantum-field-theory quantum-entanglement
73
questions
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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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2
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59
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How can I construct a trivial product state in the continuum?
When working on the lattice it is easy to define a trivial product state. A state $|\psi\rangle$ is a trivial product state if it admits the following tensor decomposition,
\begin{equation}
|\psi\...
2
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1
answer
67
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Operational meaning of mode dependence of mode-entanglement
In this paper, Vedral shows that the entanglement in second quantized states can depend on the choice of modes. As a simple example, he points out that the ground state of two non-interacting harmonic ...
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130
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Does the no signalling theorem in quantum mechanics beg the question?
I had always thought similarly and then came across a paper here that argues this.
The abstract is as follows:
Many authors state that quantum nonlocality could not involve any controllable ...
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103
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Decoherence time of quarks
I have been reading papers on using top quark's use as a probe for new physics using quantum information theoretic observables such as concurrence. One of the reasons they provide for using a top ...
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128
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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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87
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Is Von Neumann entropy in QFT related to the two-point function?
Suppose I have a scalar QFT. Is the Von Neumann entropy related to the two point function? More generally, given the two point function and an entangling surface, can we calculate the Von Neumann ...
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Resource Recommendation for Quantum Information Theory especially entanglement in quantum field theory
I am trying to start learning quantum information from a theoretical point of view not involving aspects of quantum computing. The main thing that I want to understand is entanglement from both a ...
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How is entanglement of non-spin variables incompatible with local realism?
It seems to me that spin/polarization entanglement is the only spooky one. That's because the entanglement of other observables would happen even in regular classical physics if we made a "...
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What's wrong with my argument about entanglement entropy in QFT being time-independent?
Let's say we need to compute the entanglement entropy (EE) of a subsystem $A$ ($A=[0,L]$, $L>0$) in a 2D CFT.
The density matrix of the total system (i.e., the real axis) is given by
$$
\rho(t)=\...
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Proof of the expression for entanglement entropy from correlation matrix
Let a quantum system be described by a correlation matrix
$$
C_{ij} = \langle c_i^\dagger c_j \rangle\ ,
$$
which we can split in components $A$ and $\bar{A}$. I have read that we can calculate the ...
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Is the circuit unitary in Nielsen's method for calculating complexity?
I was trying to learn how to calculate circuit complexity (1707.08570) when I chanced upon a seemingly confusing concept. The "Nielsen method" involves looking at a unitary transformation $U$...
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How to describe the entanglement in the jets?
Consider a pair of quark and anti quark flew away and generate the "jets"(whatever that meant).
But from the color conservation, it was assured that the seemly isolated jets that was ...
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Can we determine when the lowest-energy state cannot be annihilated by any local operator, just by inspection of the Hamiltonian?
Relativistic quantum field theory (QFT) has the property that the lowest-energy state cannot be annihilated by any operator that is localized in a finite region of space (references 1,2,3). In other ...
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Hamiltonian basis in multiple particle systems
I have a question about the choosing of basis that compose the Hamiltonian of multiple systems. For example if we have a system of N particles, that depend in our case of Pauli matrixes i will give ...
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Is it possible to peform thermodynamic work by harvesting entanglement from the vacuum?
I have already asked two questions on this topic:
1. What happens to the vacuum when entanglement is harvested? [closed]
and
2. Does entanglement harvesting require cooling the environment to ...
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295
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Good book to study entanglement in detail
Can anybody suggest a good book to know about quantum entanglement? I am a master's student and I have good knowledge of quantum mechanics. I want to know more on this subject. It would also be useful ...
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Why does the no-cloning theorem imply the monogamy of entanglement?
I have seen papers where they mentioned that the monogamy of entanglement can be seen as a consequence of the no-cloning theorem. Could somebody sketch this out?
N.B.: I have seen the argument that ...
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Constructing orthonormal bases in sub-Hilbert spaces of $L^2(\mathbb R)$ defined for particular spatial regions?
I've explored the entanglement of modes by expanding the ground-state solution of a many-body problem as an infinite sum of Slater determinants of one-particle Hermite functions. The one-particle ...
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67
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Can you entangle two electrical fields?
Lets say I have two already existing electrical fields. can I entangle them and cause one to influence another. (see image)
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416
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What happens to the vacuum when entanglement is harvested?
I stumbled upon this website which talks about entanglement harvesting. I also already asked a question on this subject regarding some experimental question. In this post I want to ask another ...
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Does entanglement harvesting require cooling the environment to sufficiently low temperatures?
I stumbled upon this webpage, which describe a process they call "entanglement harvesting". I was wondering whether to observe this effect it is necessary to cool the environment to ...
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Is incompatibility required for contextuality?
A preprint just came out claiming that incompatibilty is not requried to demonstrate generalized contextuality. My question isn't about generalized contextuality---which I don't quite understand---but ...
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Why are maximally entangled continuous variable states not physical?
I have been going through this paper: https://arxiv.org/abs/quant-ph/9908056
There in, just after eq (1), it's mentioned that maximally entangled continuous variable states are not physical. Why is ...
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How does QFT explain QM phenomena?
I've been studying QFT for a couple of years now, and until today I haven't encountered any of the phenomena that I've studied in my QM course: tunneling, entanglement, probability measurements and ...
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How can anything be unentangled?
If the universe is made of fields that exist everywhere, won’t every point in the universe become entangled with those around it, expanding out at the speed of light? How could two systems nearby one ...
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The emergence of space-time from entangled states
I recently read an article by Yasunori Nomura (https://arxiv.org/abs/1711.05263), in which he says that space-time is an emerging phenomenon. At the same time, space-time disappears when the ...
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Changing the relative phase of two photons in an Hong-Ou-Mandel interference produces anti-bunching?
What happens to the output of a beam splitter when you change the relative phase between two photons that enter from the two input ports?
In Hong-Ou-Mandel interference for a beamsplitter of the form, ...
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What is the form of a many-body hamiltonian that are subject to the measurement of the position?
Suppose there is a $N$ body hamiltonian, suppose $N=2$ for simplicity:
$$
H = - \frac{1}{2} \nabla_1^2 - \frac{1}{2} \nabla_2^2 + V(r_1,r_2) + \frac{1}{|r_1 - r_2|}.
$$
If we make a measurement for ...
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131
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Why does the entanglement of quantum fields depend on their distance?
When watching Seans Carrol's "A Brief History of Quantum Mechanics", he mentioned around the 50th minute (the video I linked to starts at that point) that
[about quantum fields in vacuum] .....
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Are equal-time commutators well-defined in QFT?
I'm working through some QFT course notes and I just want to check that my understanding of equal-time commutators is correct.
I don't have much to go on -- the notes rather cryptically insert the ...
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127
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Quantum Bayesianism and Bayesianism [closed]
I am studying both Quantum Bayesianism (QBism) and Bayesianism (the idea that probability is subjective). I am wondering if QBism and Bayesianism face the same objections and lead to the same problems ...
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225
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Quantum Bayesianism and the Copenhagen interpretation
Is Quantum Bayesianism (QBism) preferable than the Copenhagen interpretation of QM?
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Implications of MIP*=RE for physics?
Background
Earlier this month (Jan 2020) a pre-print was posted to the arXiv claiming to have proved the equivalence of the complexity classes $\mathrm{MIP}^{*}$ and $\mathrm{RE}$ (see below for ...
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Do "delayed choice" experiments send information back in time?
Consider the wave function collapse of a pair of entangled photons:
wave function is collapsed, let's call this state '0'
normal wave function, let's call this state '1'
In a "delayed choice" ...
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Are photons locked in time, and does this explain the "delayed choice quantum eraser" experiment?
I'm trying to wrap my head around the "Delayed Choice Quantum Eraser" experiment and how events in the future affect light in the past.
I'm sure I'm wrong but to me this seems to indicate that ...
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292
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QFT: the origin of vacuum correlation
My question is about the origin (or mechanism?) of vacuum correlation.
In quantum field theory in flat spacetime, a free scalar field has the following two-point correlation function at the same ...
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Quantum Non-Demolition of entangled superposition using an electron with infinite spin
Disclaimer: I have no idea what I am talking about, as I just started college and barely understand quantum physics.
If an electron can have a linear velocity of the speed of light, theoretically ...
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Holographic entanglement entropy (Thermal case)
I'm trying to calculate the entanglement entropy in CFT2/AdS3 in the thermal case for a finite interval (-a,a). I'm reading the paper of Takayanagi and Rangamani (2016): https://arxiv.org/abs/1609....
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Can I raise a quantum mechanical operator to another quantum mechanical operator?
The most complicated power operation for operators that I have seen is an operator (or a sum of operators) raised to a number. How can I handle an operator raised to another operator? Is this even ...
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Critical parameter for 1D quantum system corresponding to $T_c$ of 2D Classical model
Utilizing the fact that there is a correspondence between a $d$ dimensional quantum system and a $d+1$ dimensional classical system (c.f. Trotter Decomposition), my question regards what the critical ...
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350
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What is the relationship between spin network spacetime and tensor network (entanglement) spacetime?
In 1971, Sir Roger Penrose, suggested a combinatorial construction of spacetime using the angular momentum of particles. This work led to and introduced the idea of spin networks which are ...
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Quantum entanglement in QFT [duplicate]
What is the explanation of the quantum entanglement in the quantum field theory framework?
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Status of entanglement/black hole entropy in quantum field theory
It used to be said that in QFT, black hole and entanglement entropy is overcounted because entropy turns out to depend on volume, even if we somehow eliminate infinities.
Does this assessment still ...
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Can the entanglement entropy of a ground state scale extensively?
To my knowledge, entanglement entropy (EE) for the ground state of a many-body system scales subextensively, that is:
\begin{equation}\lim_{\text{Vol}_A \to \infty} \frac{S_A}{\text{Vol}_A}\to 0.\end{...
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Can we always find a Hilbert space corresponding to a region of spacetime?
In defining entanglement entropy in field theories we take a region A in spacetime. Now if $\mathcal{H}$ is the Hilbert space of the field theory we assume that we can decompose this Hilbert space ...
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778
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Quantum entanglement in quantum field theory
How is entanglement described in quantum field theory? For example, if a fluctuation in the electron field represents an entangled electron, is there an equal and opposite fluctuation in the positron ...
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Spin operator for an ensemble
Given that there are N number of particles and for each one of them $\hat{\sigma}_x$ is the usual Pauli matrix. How can we show that the Pauli matrix for the entire ensemble has the form $\frac{1}{N}\...
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What happens if you make an observation of the spins of two entangled, far apart electrons at exactly the same time? [closed]
If we consider the spins of two, far apart, entangled electrons, what will happen if we make a measurement on both spins at exactly the same time (let's assume time is not discrete)? I see it as a ...
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Microstates associated to Von Neumann entropy/Entanglement entropy
I was wondering if one can see entanglement entropy as a way to count microstates and if so what exactly are the microstates? Usually when one talks about entanglement entropy, one thinks of it in the ...
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