Quantum mechanics describes the microscopic properties of nature in a regime where classical mechanics no longer applies. It explains phenomena such as the wave-particle duality, quantization of energy and the uncertainty principle and is generally used in single body systems. Use the ...

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23 views

Expectation Value of Unitary Time Evolution Operator in Quantum Mechanics

Does the expression $\langle \Psi_i|U(t)|\Psi_i\rangle$ have a specific meaning, where $U(T)$ is the unitary time evolution operator of $\Psi$, and $\Psi_i$ is the initial state of $\Psi$? If so, ...
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14 views

Relationship between the g-factor and the gyromagnetic ratio?

From what I have read the g-factor and the gyromagnetic ratio are two different quantities. It appears to me that the gyromagnetic ratio is the ratio between (any) angular momentum and the magnetic ...
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0answers
12 views

Generators of cubic group: Euler angles

I am trying to build numerically all members of the cubic group in the representation of Wigner D matrices. Angular-momentum quantum number may be small, e.g. 2, so I use the formula stated e.g. at ...
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16 views

measurement of tripartit qubit state

From general schmidt decomposition, GSD, the state of tripartite is classify by five parameter as below: |V>=a|000>+b|100>+c|110>+d|101>+e|111>. how can I determine the value of parameter a,b,c,d,e? ...
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4answers
136 views

Basis independence in Quantum Mechanics

The idea that the state of a system does not depend on the basis that we choose to represent it in, has always puzzled me. Physically I can imagine that the basis ought to just yield an equivalent ...
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0answers
41 views

The link between non-locality and Heisenberg's uncertainty relations

I have recently found out1 that the concepts of non-locality and Heisenberg's uncertainty do not live independently of one another in Quantum Mechanics. In other words, roughly the idea goes as: the ...
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21 views

local unitary transformation

From my reading, local unitary representative by unitary operator, U that Hermitian. Can anyone give me an example of tripartite qubit that undergo the local unitary tranformation with unitary ...
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2answers
58 views

Eigenvalue physical meaning [on hold]

What is the physical significance of eigenvalues or eigenvectors?? Please try to explain in very simple language simple harmonic oscillator , potential well could you support your answer by ...
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3answers
72 views

Quantum Entanglement - Problem with Bell's Inequality?

To ask the question, I will state the scenario first. Please let me know if the scenario is not described appropriately. The question is in the scenario itself. There are many questions marks in this ...
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1answer
42 views

Difference in Raman, Rayleigh, and Compton scattering

I'm studying modern physics and have some questions about these three different scattering. In the book and wiki all tells me Raman and Rayleigh scattering are inelastic and elastic collision ...
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1answer
29 views

Time-Evolution of a Spin-1 Particle in a Magnetic Field

A spin-1 particle with charge $q$ and magnetic moment $\vec{\mu}=\frac{gq}{2mc}\vec{S}$ is situated in a magnetic field $B=B_0\vec{z}$. At $t=0$ the particle is found in an eigenstate $\hat{S}_y$ with ...
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43 views

Time-Evolution of a 3-State System

The Hamiltonian for a three-state system is, in some basis $|1\rangle ,|2\rangle,|3\rangle$ $$\hat{H}= \left( \begin{array}{ccc} E_0 & 0 & A \\ 0 & E_1 & 0 \\ A & 0 & E_0 ...
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57 views

Can I *always* decompose a normalizable function into the discrete Hydrogen spectrum?

This question has been bothering me for a while now: can one reconstruct an arbitrary (normalizable) function $\phi(\mathbf r)$ in $\mathbb R^3$, with only the discrete set of Hydrogen wavefunctions ...
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44 views

Atom - light field coupling and emission process

Suppose a "2-state atom" and a light field are quantized with the following Hamiltonians, respectively: $$\hat{H}_A=\hbar\omega_{21}\hat{\sigma}^{\dagger}\hat{\sigma}$$ and ...
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36 views

Is mass in the sub-atomic particles caused by their angular momentum? [on hold]

When they found the God Particle, they said it's responsible for creating mass in all other particles except photons and neutrinos. But how it creates mass is a mystery to me. My suspicion is that ...
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20 views

Deriving Wave Function for Scattering States with Delta-Function Potential

I am following the Griffiths Book on Quantum Mechanics, and am following the derivation for the wave function for Delta-Function Potentials. $$V(x) = -\alpha \delta(x)$$ In the scattering states, ...
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62 views

Bohr on wholeness?

I vaguely remember that it was Bohr who insisted that in a quantum experiment the whole experimental situation (but excluding the classical preparation and detection devices) must be considered as a ...
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27 views

Fermi's theory of beta decay - Does Fermi's Hamiltonian have the wrong transformation properties?

I'm studying the theory of beta decays as proposed by Fermi in the 30's, and I found an inconsistency between the transformation properties that he claims for his Hamiltonian and the transformation ...
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1answer
45 views

Shouldnt atoms of same elements repel each other?

Shouldnt the same type if atom repel each other because of electrostatic charge.
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22 views

1D Harmonic Oscillator: Eigenstate (|x=0>) at position x=0

Given an harmonic oscillator I need to calculate the eigenvector $|x=0\rangle$. Knowing that $$x|x=0\rangle = 0 \quad \Rightarrow \quad (a + a^\dagger) | x = 0 \rangle = 0 $$ I started to plug in the ...
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0answers
21 views

How does a Collider work? [on hold]

How does a collider work, explained using various Physics theories (or if there is a main one) . How does the acceleration play a part in the individual sub-atomic kinetic levels. What happens when ...
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3answers
133 views

Momentum operator representation

If $\hat{p}$ acts on position eigenstate, it is $$\tag{1}\hat{p}\left|x\right\rangle=+i\hbar\frac{\partial }{\partial x}\left|x\right\rangle .$$ But in general $$\tag{2}\hat{p} = -i\hbar ...
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67 views

The $I_{3322}$ Inequality

I am trying to understand the $I_{3322}$ inequality which is an another example of Bell inequalities and which is different from the famous CHSH inequality. I haven't got hold of any standard ...
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1answer
35 views

How to show the finite rotation of a spin-1/2 system?

I'm reviewing my quantum mechanics by going through Sakurai and Napolitano again and working out all of the derivations. I'm stumped (though I probably shouldn't be) on some algebra in the finite ...
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1answer
101 views

Quantized light-atom Hamiltonian

Suppose a "2-state atom" and a light field are quantized with the following Hamiltonians, respectively: $$\hat{H}_A=\hbar\omega_{21}\hat{\sigma}^{\dagger}\hat{\sigma}$$ and ...
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25 views

Could my idea of Faster-Than-Light communication using quantum entangled particles be feasible? [duplicate]

I am most likely completely off but I have an idea on how we might be able to exchange information using spins only (provided that we prepare for the exchange of information): We communicate using ...
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2answers
121 views

How does the Physics work for the Quantum Suicide thought experiment?

On page 5 of this paper written by Max Tegmark, Tegmark discusses a thought experiment called 'Quantum Suicide'. As far as I understand it, this experiment was created to show the experimental ...
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1answer
41 views

What is meant by taking the partial derivative of the Hamiltonian in this situation?

I'm doing a computation involving the quantum mechanical harmonic oscillator, and I have an expression of the form $\frac{\partial}{\partial \omega} \hat{H}$ where $$\hat{H} = \frac{1}{2m} \left( - ...
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41 views

Landau levels in uniform magnetic field

Intro Landau levels are obtained by gauging the vector potential to be $$ \vec{A}=\left(-By,0,0\right) $$ By which the Hamiltonian: $$ H={1\over 2m}\left(\vec{p}-q\vec{A}\right)^2 $$ can be ...
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2answers
78 views

According to many worlds interpretation, to which world will I go?

From my understanding, many worlds interpretation views the actual world (universe) has many branch points. For example, coin flipping may cause two outcomes, but I will experience only on outcome or ...
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0answers
20 views

Implications for measurement of an initially localized free particle's wavefunction spreading out to infinity?

So, I have been attempting to wrap my head around what happens to a free particle that is initially localized to one spot. It seems that due to their different frequencies, the particle's wavefunction ...
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4answers
590 views

Why do electrons jump between orbitals? [duplicate]

When an electron is excited to higher energy levels, it will jump back to the same level from which it was excited. Why does it develop "sentiment" with that level?
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1answer
22 views

Implication of rotational symmetry on scattering matrix/ scattering cross-section [on hold]

How does the rotational invariance helps simplifying Non-relativistic quantum scattering problems? Is there any any additional information that can be extracted about the scattering amplitude? It ...
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0answers
46 views

What does representing position as a function of frequency mean? [on hold]

I am doing an introductory course in quantum physics. A part of the magical paper of Heisenberg says, "For a state characterized by the label $n$, the fundamental frequency $v(n)$, and the ...
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31 views

Can we generate artificial electrostatic energy? [on hold]

Can we generate artificial electrostatic energy for electrostatic attraction?And can it be controlled to get element specific electrostatic attraction?
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3answers
192 views

How can I solve this quantum mechanical “paradox”?

Let a (free) particle move in $[0,a]$ with cyclic boundary condition $\psi(0)=\psi(a)$. The solution of the Schrödinger-equation can be put in the form of a plane wave. In this state the standard ...
3
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1answer
100 views

How I can prove the Commutation between hamiltonian and Runge-Lenz vector? [on hold]

I am a undergraduate student in physics. I found this page that shows a way to prove the commutator between Runge-Lenz vector and Hamiltonian .$\left [\hat{A}_{i},\hat{H}\right]=0$ I believe he did a ...
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167 views

Has Jaynes's argument against Bell's theorem been debunked?

As a student of theoretical physics I'm well acquainted with the multitude of crackpot ideas attempting to circumvent Bell's theorem regarding local hidden variable theories in quantum physics. ...
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117 views

Single quantum particle in beam splitter, with different systems located in each channel

Suppose a quantum mechanical particle enters a beam-splitter, which sends its wave packets into two mutually orthogonal channels, $C_a$ and $C_b$. Suppose that $C_a$ also contains System A, with ...
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34 views

Proof that a Hermitian Matrix is not defective?

I am taking an introductory course into Quantum Mechanics. To me to seems pretty simple to prove most properties of Hermitian operators. However, I am stuck at an edge case, proving that if an ...
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1answer
26 views

Generate exciton with parallel/anti-parallel spin

How can I experimentally generate excitons, controlling the spin-polarization of the participated electron and hole to be either exclusively parallel or anti-parallel?
2
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4answers
149 views

Regarding the usage of 'classical potentials' in quantum mechanics

I am familiar with basic quantum mechanics and I know that there is no concept of 'force' in quantum mechanics, unlike in classical mechanics. Problems in quantum mechanics are solved by writing down ...
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1answer
38 views

Thomas-Fermi approximation for cold atoms in a 1D harmonic potential

The Time-independent Gross-Pitaevskii equation is $$ \mu{\phi(x)}=\Big(\frac{-\hbar^{2}}{2m}\nabla^{2}+V_{ext}(x)+g|\phi(x)|^{2}\Big)\phi(x) $$ From Thomas-Fermi approximation, $$ ...
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1answer
56 views

Density matrix from Wigner distribution

Density matrix or Wigner function can be defined from the other with Fourier (or inverse) transformation. equivalently the value of W(q,p) can be seen as the mean value of the displaced parity ...
0
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1answer
84 views

Is a larger black hole a faster or a slower processor?

For a remote observer, a black hole with mass $M$ has a temperature $T=1/M$. Now I am confused with the problem: A larger black hole can achieve a task faster or slower if it's regarded as a kind ...
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35 views

How does Loop Quantum Gravity describe particles? [duplicate]

What are elementary particles according to Loop Quantum Gravity?
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4answers
134 views

Is what statisticians call a “random variable” what physicists call an “observable” in QM? [duplicate]

I read at http://www.statlect.com/fundamentals-of-probability/random-variables that A random variable is a variable whose value depends on the outcome of a probabilistic experiment. Its value is ...
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1answer
43 views

Why does quantum mechanics produce different predictions for Bell test experiments than classical mechanics?

I understand that experimental results from Bell test experiments have shown that measured correlation is a cosine function of the angle between the detectors. What I am struggling to grasp is why ...
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1answer
64 views

Conservation of momentum in infinite square well

This is inspired by Griffiths QM section 2.2, on the infinite square well, which is about how far I've gotten (so, sorry if this is addressed later in the book). For any given starting wavefunction, ...
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58 views

scientific theory [closed]

According to Einstein, any scientific theory should have a mental image like raiding alongside a beam of light, free fall from a tower etc. He said "If a theory doesn't have a mental image that even a ...