# Tagged Questions

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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69 views

### Identifying fragments when there is a superposition of fragments in quantum Darwinism

In Zurek's theory of quantum Darwinism, information about the pointer states of a system imprint themselves upon fragments of the environment carrying records about the state of the system. ...
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110 views

### Quantum circuit decomposition

I need to construct a universal quantum circuit decomposition for a three-qubit operation where one qubit is the control bit, and a two-qubit unitary operator acts on the other two depending on the ...
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17 views

### Showing that the CHSH inequality is not violated

I can usually work out whether CHSH inequality is violated when the observables that we are measuring and the state we are in is given explicitly, but I'm struggling with the generality of the ...
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34 views

### What does the difference in odds for Bell's inequality tell us about quantum mechanics?

Bell's inequality defines a lower bound for agreement/disagreement between entangled particles. When the experiment is conducted it shows lower odds. What does this tell us? Is it possible that we ...
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36 views

### Question regarding operators and cylindrical coordinates

I have the following problem in my hand: I need to arrive from the Cartesian expression $$x_{j}{\partial_{k}}x_{j}{\partial_{k}}-x_{j}{\partial_{k}}x_{k}{\partial_{j}}$$ to this expression: ...
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41 views

### Why doublons and holons are not bounded in spin-1/2 Hubbard chain?

The Hubbard model reads $$H = -t \sum_{\langle ij \rangle, \sigma} c_{j\sigma}^\dagger c_{i\sigma} + U\sum_i n_{i\uparrow}n_{i\downarrow}$$ In the large $U$ limit and at half-filling, the Hubbard ...
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18 views

### Degeneracy of orbitals in magenetic field

Why is that in an external magnetic field(uniform) the degeneracy of d,f orbitals is lost but the degeneracy of p orbitals remain intact assuming the main cause of losing degeneracy is the difference ...
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51 views

### The gauge-invariance of the probability current

It is simple to show that under the gauge transformation \begin{cases}\vec A\to\vec A+\nabla\chi\\ \phi\to\phi-\frac{\partial \chi}{\partial t}\\ \psi\to \psi ...
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31 views

### Physical significance of effective wave function

In Yanhua Shih's book on quantum optics, the coherence functions are expressed in terms of effective wave function. Here are the expressions for single photon wave packets. To derive the coherence ...
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21 views

### What does it mean to erase the which-path information of something?

In this particular case, I am told that very fast measurements erase which-path frequency information of photons. I'm not really sure what that means though. I do not entirely understand the concept ...
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62 views

### What does this notation mean in terms of quantic numbers, and how to imagine the electrons in this quantic system? (Helium $2^1$ $P$ and $2^3$ $P$)

Helium atom in the $2^1$ $P$ and $2^3$ $P$ excited states Now I'm guessing that 1 electron should be considered in the 1s state, but what about the other? Should I consider the other as simply ...
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51 views

### Hamiltonian matrix propertu

A professor made an statement to prove the variational theorem: Because the Hamiltonian (H operator of quantum physics) is diagonal in its own eigenfunction, the terms in \$\left \langle \Phi _{m} ...
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47 views

### Finding the coefficients of a spinor

From the Schrödinger equation of a system I'm investigating, where the wave function is a 4-component spinor of coefficients $C_1, C_2, C_3, C_4$, I am able to obtain the expression \$\begin{pmatrix} ...
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80 views

### Quantum uncertainty can explain the Riemann Hypothesis?

In the recent paper "Riemann Hypothesis as an Uncertainty Relation" (http://arxiv.org/abs/1304.2435) the author claims that the presence of zeros out of the critical line may lead to the violation of ...
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42 views

### Partial Measure Probability

Let be a $$|\psi\rangle = \dfrac{3}{5\sqrt{2}}|00 \rangle- \dfrac{3i}{5\sqrt{2}}|01 \rangle+ \dfrac{2\sqrt{2}}{5}|10 \rangle - \dfrac{2\sqrt{2} i}{5}|11 \rangle$$ state with two qubits. ...
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32 views

### The physical implementation of quantum annealing algorithm

From that question about differences between Quantum annealing and simulated annealing, we found (in comments to answer) that physical implementation of quantum annealing exists (D-Wave quantum ...
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27 views

### Partial Measurement in Computational Basis

I am reading my lecture, here say: For example, we can measure the first qubit of system described by the state \$|\psi\rangle = \sqrt{\dfrac{2}{3}}|0\rangle \otimes \dfrac{|0\rangle - ...
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57 views

### Quantum harmonic oscillator. Finding operators

Problem: I'm trying to verify that $p_H(T)$ and $x_H(T)$ satisfy the following equations, (by solving the Heisenberg equation): $x_H(t)=x_H(0)cos(\omega t)+(1/m\omega)p_H(0)sin(\omega t)$ ...
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40 views

### Wave equations for two intervals at Potential step

Lets say we have a potential step as in the picture: In the region I there is a free particle with a wavefunction $\psi_I$ while in the region II the wave function will be $\psi_{II}$. Let me ...
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33 views

### Is it easier to determine the number of states with raising/lowering operators or using scattering?

A particle is bound by $$V(x) = \begin{cases}\infty,& x <0 \\ \frac{-32\hbar^2}{ma}, & x\le a \\ 0, & x \le a\end{cases}$$ a) how many states are there? i'm attempting ...
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35 views

### Do the other properties of a particle also have a phase?

Particles have a phase that oscillates in space-time. We know this because particles have a phase frequency (De Broglie wavelength) and this is why they interfere in space, like in the double slit ...
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94 views

### Wave function ansatz for disclinated graphene with spin

I am currently investigating spin dynamics in disclinated graphene. More information about my approach can be found in my other post. I would like to know if my approach is somewhat correct to find ...
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34 views

### Landauer's principle vs Rayleigh–Jeans law

Can we argue based on Landauer's principle that if one bit information is changed inside a blackbody, the total radiated energy should be at least or in order of $kTln2$? If it is so, can we also ...
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44 views

### How large must the Quantum teleportation fidelity have to be in order for it to be useful?

This question relates and stems from my original question. Please read this one and the comments before answering this question. Quantum Teleportation Fidelity I know that for discrete variables ...
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72 views

### Impulse travelling faster than light

There have been conducted many experiments in which light impulses traveled faster than light like the one in Princeton in 2000. This phenomenon has something to do with quantum entanglement. Does ...
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39 views

### Photon detection rate for pure / mixed states coming from single mode point source

Let the pure states be in superposition of horizontal and vertically polarized basis states. They are arriving at the point detector one at a time. So, a pure state is \$|\Psi\rangle = \alpha|V\rangle ...
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29 views

### Thermionic emission, delayed emission and predissociation

In molecular photodissociation, the thermionic emission, delayed emission and predissociation are the same? otherwise, what is the difference between them? My question is not about the solids, but I ...
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55 views

### Did Planck said that his theory is distinct from Zeno's paradoxes?

I remember once reading that Planck or some other prominent figure in quantum physics said that the theory (probably Planck length or Planck time in particular) is not about the thing what Zeno's ...
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31 views

### Implication of Fock matrix elements

In linear combination of atomic orbitals/molecular orbital based quantum chemistry theory, when the block of Fock matrix elements connecting occupied with virtual orbitals is zero, why does this imply ...
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42 views

### Why People talk so much about Feshbach resonance while dealing with Bose-Einstein Condensate (BEC)?

Why People talk so much about Feshbach resonance while dealing with Bose-Einstein Condensate (BEC)? Why not tune the system near the resonance and measure the effect on BEC formation?
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17 views

### Allowed Quantum States- Filkelstein and Rubinstein constraints

So basically i'm doing a report on Finkelstein and Rubinstein constraints. I have a system where the allowed quantum states satisfy ...
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33 views

### Where can I find the Bohr Sommerfield condition?

I need to solve the Hydrogen Atom using the phase integral [Bohr Sommerfield Condition] but I don't know where can I find it. Help me please!
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37 views

### Rotating Frame with degenerate levels

I'm working with a angular momentum transition J=0 -> J=1 with no applied magnetic field; so, the upper level has degeneracy 3. This atom is coupled with an electric field propagatin in the ...
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77 views

### Quantum mechanics, whats possible?

There is a thread in Physicsforums.com which states due to Quantum Mechanics, if you wait long enough diamonds will appear in your pocket, it also states its possible for all your atoms to ...
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102 views

### Polarization photon and Stokes parameters

I have the following situation: About the polarization of the photon, I introduce the basis: Horizontal polarization $|\leftrightarrow>=\binom{1}{0}$ Vertical polarization ...
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36 views

### reference for wavepackets and uncertainty relation

Can someone suggest a reference for a rigorous proof(from harmonic analysis) that for any wavepacket other than the gaussian, we have an inequality ie \delta x \delta k > 1
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55 views

### Why is the transition into N proportional to N+1?

I am having trouble understanding the origin of the bosonic stimulated emission. How can I qualitatively understand why bosons Boson's attract each other into similar quantum states. The furtherst I ...
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57 views

### What is the link between the density matrix and Hestenes' spinors in geometric algebra?

The density matrix (or state matrix) is a generalization of a wave function that is able to describe incoherent superpositions of an N-state system. It is often written as a matrix and observables are ...
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111 views

### Phase diagram problem for ternary system

For a ternary system, three composites are present. Temperature is also a variable. Assuming that pressure is held constant, what is the minimum number of phases that may be present in a ternary ...
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18 views

### Is there a way to compute or explain if a decay prefers decaying into mainly mass or mainly energy?

Is there a way to compute or explain if a decay prefers decaying into mainly mass or mainly energy ? I know quarks prefer to decay into the most massfull quarks : ...
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45 views

### Dilatations in non-relativistic QM and operator tranformation

I was looking at a QM textbook exercise dealing with dilatations, the transformations are $x \rightarrow x' = \lambda x$ transforming $|\psi\rangle$ into \$|\psi'\rangle = ...
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27 views

### How to find relaxation matrix?

Could anyone help me to understand how to derive equation 9 from 8 in this article I am reading? I am not getting about the matrix $R$, Super operator $\Gamma$.
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139 views

### Newton Gravitational constant $G$, Plank constant $\hbar$ , Speed of Light $c$ : The Dream Team of moderators?

The 3 great constants of Nature are well known : The Speed of light $c$ (special relativity) The Plank constant $\hbar$ (quantum mechanics) The Newton ...
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33 views

### motivating theories structurally from operationalism, not from underlying structured sets (Categorifying Operationalism and Abramsky's Chu spaces)

We normally construct theories by presuming underlying sets, such as sets of space time points, or sets of vectors in a Hilbert space. I think you can show that leads to weaknesses of realism (see ...
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93 views

### Direction vector of a physical quantity matrix

A physical quantity can be represented by the following form: $A = a_1\sigma_1 + a_2\sigma_2 + a_3\sigma_3$ where $\sigma$ matrices are Pauli matrices. Also suppose that there is \$B = b_1\Sigma_1 + ...
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152 views

### Connection between first and second quantization

This is my question: In a book on many body quantum theory I came across equality between antisymmetrized many-particle state vector which, as you know, includes sum over permutations of product ...
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80 views

### Quantum Mutual Information scaling

Wikipedia provides a simple definition of Quantum Mutual Information: $$I(\rho^{ab})= S(\rho^{a}) + S(\rho^{b}) - S(\rho^{ab})$$ where in terms of relative information we have: I(\rho^{ab})= ...
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203 views

### Intensity of the diffraction pattern of the double slit

I am trying another approach for my last unanswered question. (Bounty still on for 3 days. Anyone? Please?) Note that this is not the same question but a greatly simplified version concerning a much ...
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53 views

### Counterpart of the  Klein Gordon Equation on the “Coordinate Shell”

The relation $$\psi=Ce^{i/\hbar(Et-\mathbf{p}\cdot\mathbf{x})}\tag{1}$$ satisfies the Klein Gordon equation on the mass shell, i.e. for $E^2=p^2+m^2$. Now let's think in the reverse direction. ...
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102 views

### Can experiment distinguish the basis in which a singlet state is represented?

Let $\left(|\uparrow\rangle,|\downarrow\rangle\right)$ and $\left(|\nearrow\rangle,|\swarrow\rangle\right)$ be two bases of the $2$-dimensional Hilbert space $H$. Can an experiment distinguish ...
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