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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plane wave state used for scattering calculation

When we do scattering calculation off a potential barrier, normally we would assume some incident plane wave and then make use of the boundary conditions. But how is this corresponding to the ...
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1answer
29 views

Quantum anharmonic ocscillator $E_0(\lambda)$ curve or table

I am looking for the exact data on $E_0(\lambda)$ for the anharmonicity $\lambda x^4$. The perturbative expansion is the following: $E_0(\lambda)\approx 0.5(1+1.5\lambda -5.25\lambda ...
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1answer
21 views

One dimensional scattering cross section

My quantum mechanics book (http://www-thphys.physics.ox.ac.uk/people/JamesBinney/qb.pdf, pages 94-95 of the pdf, or 86-87 of the book) considers the one dimensional step potential ...
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2answers
47 views

How does light oscillate?

Why do we say that electromagnetic wave is oscillating? Or does light propagate really in a wavy form like this image? What is making the photons oscillate and how is it oscillating is it ...
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17 views

What are the reactions that take place inside battery at the quantum level?

I was just studying about how a battery works on the internet and found out that there are reactions of chemicals which make the electrons move. But what exactly happens inside a battery (lets take a ...
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2answers
36 views

Is it possible to make an electromagnetic shield?

Is it possible to make an electromagnetic shield to protect something (or ourselves) against things like bullets, human attacks, metals thrown on us or simple dust particles to protect a spaceship ...
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1answer
44 views

How can we prove this system is in a stationary state?

I'm having trouble using the given hint to solve the problem. The problem statement is as follows: At instant $t=0$, the probability distribution of a particle under a potential $V(x)$ is ...
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1answer
30 views

How to solve infinite square well with exponential solution (of oscillatory type)?

Given a potential well of $V = 0$ on the interval $(0,L)$ and $V = \infty$ outside the well, I am working to solve the Time Independent Schrodinger Equation $$\dfrac{d^2}{dx^2} \psi= ...
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1answer
45 views

Can an Atom be negatively as well as positively charged simultaneously?

For example there are three atoms- atom A, atom B, atom C. Atom A has 3 electrons, atom B has 4 electrons and atom C has 2 electrons. If we bring together atom A and atom B, in this case atom A is ...
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26 views

Accuracy of quantum mechanical algorithms

Is it possible for a quantum mechanical algorithm to ensure when the wave function collapses that the right answer will be obtained 100% of the time? For this, I am excluding processes such as ...
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2answers
61 views

The equivalence between Heisenberg and Schroedinger pictures

In quantum mechanics, the two pictures of Schroedinger and Heisenberg are taken as equivalent, where in the former wavefunctions are time variants and operators are not, and in the latter it is the ...
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1answer
43 views

Does a photon travel in all directions?

For example i am standing and a beam of light is passing in front of me. I am able to see that beam of light so does it mean that photons are travelling in all directions other than the photons which ...
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2answers
38 views

Is the interference quantum mechanical superposition the same as entanglement? [duplicate]

Are the interference of two wave functions an equivalent way of saying that they are entangled?
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20 views

Orthogonality preservation vs. preparing a state

I'm trying to learn the fundamentals of quantum theory, lately mostly using the lectures by Prof. Susskind which Stanford University made available on Youtube. Here is one thing I have trouble ...
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2answers
80 views

What is the Hermitian adjoint of operator $\hat{K}\psi = \psi^*$?

For many operators, their adjoint can be expressed as a function of other known operators, for example $$\hat{T}_a^\dagger = \hat{T}_{-a} \\ \hat{p}_x^\dagger = \hat{p}_x$$ where $\hat{T}_a \psi (x) = ...
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17 views

Valence bond wavefunction of nitrogen

Could someone explain to me how one finds the valence bond wavefunction of an atom? Take nitrogen for example, I know both nitrogen molecules have a valence-electron configuration of 2s22p1x2p1y2p1z ...
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Stress testing Quantum Uncertainty, a multi Phase Question

I start this line of thinking, and i begin to seek the right questions to ask. I am of humble origin, but even here i remember that all start small somewhere. I think that even the greatest minds ...
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3answers
58 views

What is $E$ in the Planck-Einstein relation?

The Planck-Einstein relation was first given for photons $$E = h\nu$$ But later, de Broglie extended it to matter waves, and showed that it would hold for all particles as well. The $E$ for a photon ...
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1answer
26 views

How to pull out the momentum operator?

In the equation (1.7.17), how does operator $p$ get out of the bracket without any operation though $<a | $, $| x'>$ are function of $x'$? How to prove this?
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1answer
41 views

What are these wavish patterns around atoms on microscopic images?

This is an IBM movie about how they move single atoms: http://www.youtube.com/watch?v=oSCX78-8-q0 There are often some "wavish" pattern around atoms on these pictures, like below some of them marked ...
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2answers
74 views

Violation of Pauli Exclusion Principle

From hyperphysics (emphasis mine): Neutron degeneracy is a stellar application of the Pauli Exclusion Principle, as is electron degeneracy. No two neutrons can occupy identical states, even under ...
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1answer
68 views

Why does this resource say that the Schrodinger Equation can be derived? [duplicate]

http://arxiv.org/abs/physics/0610121 If this is true, why do resources say that it cannot be derived? If it isn't true, can someone explain where the above preprint is wrong? I believe that my ...
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1answer
25 views

Is there an implicit assumption that each quantum well contains a single electron only? [on hold]

Is it true that each electron can be represented as a quantum well? I had believed that each energy level was able to contain multiple states and each states were able to hold multiple electrons.
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28 views

What is the “life time” of a trapped electron?

What does it mean for an electron trapped in a quantum well to have some life time? From the context it sort of times that the electron will move out of this quantum well at some time $\tau$ later. ...
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1answer
36 views

Are The Quantum Assumptions of MBT Theory Correct?

I've become very interested in Tom Campbell's MBT Theory (Plenty of YouTube videos). I can't explain it all here because it takes a book (The one he's written). It's based on the virtual reality ...
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2answers
35 views

Starter's book on Quantum Mechanics (more general and simple books than full QM textbooks) [duplicate]

This question is a little different from other questions referring to books on QM. I ask you to tell me some books that have QM on a simpler level than that of a full course on QM. Some universities ...
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935 views

Why do lines in atomic spectra have thickness? (Bohr's Model)

Consider the atomic spectrum (absorption) of hydrogen. The Bohr's model postulates that there are only certain fixed orbits allowed in the atom. An atom will only be excited to a higher orbit, if ...
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Hadamard Gate application help

I need to prove that if you apply Hadamard gates on the input/output before and after a CNOT gate that you get the same answer as flipping the target and control qbits of a CNOT. So for example I'm ...
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2answers
49 views

Position space wave function of an electron

In Wikipedia I find the wave function of a free particle to be $$ \Psi(\vec{r},t) = A\,e^{i(\vec{k}\vec{r}-\omega t)}$$ This is is a plane wave moving in the direction of $\vec{k}$ with speed (phase ...
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31 views

Property of helium superfluid [on hold]

I learnt that in helium II every atom would have same wave function and is governed by BE statistics. does that mean all helium II atoms would vibrate in the same way in a field?
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30 views

is there any molecular transition which emits a photon in certain direction

i know molecules having magnetic moment would be aligned in certain direction but do they emit photon in any certain direction when excited? are there any molecules which would emit photon in tthe ...
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1answer
45 views

Representation of operator in “$a$-representation” [on hold]

I have an operator, $X$ say, which is given by a simple phase-shift of the annihilation operator $a.$ I've been asked to give the matrix of $X$ in the $a$-representation, but I was hoping someone ...
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1answer
77 views

Singlet state and it's expectation value

So. We have a singlet sate $$ \dfrac{1}{\sqrt{2}}(\vert\uparrow\downarrow\rangle-\vert\downarrow\uparrow\rangle)$$ And two pauli matrices for z axis - one that acts on 1st spin (lets denote it with ...
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1answer
60 views

Entanglement ladder algebra and quantization of entanglement

Usually in QFT, even optical quantum mechanics papers, usually resort to describe n-states in terms of the ladder algebra, plus a parameter for polarization, but the entanglement information is ...
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Applicability of perturbation theory

Consider some system in some initial state $|k^{(0)}\rangle$. The probability that such a state makes a transition to some other state $|m^{(0)}\rangle$ can be computed to various orders in time ...
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35 views

Fermion commutation relations QFT question [on hold]

Consider left-handed fermions in two spacetime dimensions $(t,x)$: $\psi_L=\frac{1}{2}(1-\gamma_5)\psi_D$ with $J_0^\epsilon(t,x)=\psi_L^+(x+\epsilon)\psi_L(x-\epsilon)$. (a). Use canonical ...
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28 views

Quartic interacion [on hold]

I want to change Lagrangian with coupling constant lambda in quartic interaction so that coupling constant will be negative like in unstable vacuum state. This unstable state I want to describe. Can ...
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33 views

Integration measure

Consider the field being decomposed into a orthogonal and completed basis: $\Phi(x) = \sum_n c_n \phi_n(x)$ (or $\Phi(x) = \int dk c_k \phi_k (x)$, if continuous) The notation: $\phi_n(x) = ...
5
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1answer
73 views

spooky nonlocal communication, or bad abstract?

I'm referring to this recent paper, "Experimental Proof of Nonlocal Wavefunction Collapse for a Single Particle Using Homodyne Measurements" by Fuwa et al. published in Nature Communications. ...
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1answer
39 views

Analogies between Fraunhofer diffraction and Josephson junctions

There are several analogies between diffraction patterns and Josephson junctions, especially between a double slit experiment and two Josephson junctions in a superconducting ring (like this): Both ...
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1answer
29 views

What is the definition of parity conservation?

I searched quite hard, and am still confused what is the exact definition of parity conservation? For example, we have quantum system with initial state $\Phi_i$, and after decaying it comes to final ...
2
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0answers
54 views

What does it mean “Hawking radiation is in a pure state”?

I'm trying to understand black hole paradox but I'm not sure if I understand what does it mean "Hawking radiation is in a pure state". Does it mean if Hawking radiation is in a mixed state then ...
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0answers
23 views

Minimum Uncertainty Wavepackets

I'm reading over some lecture notes on minimum uncertainty wavepackets in quantum mechanics, and I've come across a statement that I'm not entirely convinced by. My take on minimum uncertainty states ...
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1answer
35 views

Can we say an atom is ferromagnetic?

Some atoms have nonzero magnetic moments. Does it make sense to say they are ferromagnetic? Or should we say it is paramagnetic?
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0answers
51 views

Anomaly for Majorana fermion?

In 4-spacetime dimension, is there U(1) gauge field chiral anomaly associated with Majorana fermion (or I am not sure if it is equivalent, majorana representation)? Besides, I have read from several ...
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0answers
56 views

Are the particle-wave duality and the quantum uncertainty principle united? [duplicate]

In a recent paper by Patrick Coles, Jedrzej Kaniewski, and Stephanie Wehner at the Centre for Quantum Technologies at the National University of Singapore, they came to the conclusion that the ...
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0answers
31 views

Help a layperson out here [on hold]

Lately I have been at it, from my completely laypersons understanding of QM with what I see si fi wooers simply replacing a God watchmaker with a cosmic Bill Gates in place of this. Help me clear this ...
3
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4answers
220 views

Understanding the Quantum Vacuum State [duplicate]

In terms of the creation and annihilation operators $a_{j}$ and $a_{j}^{\dagger}$ (fermionic or bosonic, doesn't matter): Is the vacuum state $\mid\mathrm{vacuum}\rangle$ exactly the zero vector on ...
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52 views

$n^\text{th}$ operation of creation and annihilation operators on vacuum

My question is similar to the that posted in this link. In particular I would like to express the following expression in the most compact form: $(\hat{a}^\dagger(x)+\hat{a}(x))^n\vert0\rangle$, ...
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1answer
28 views

Does a time-varying intensity contribute to the photoelectric effect?

I understand the photoelectric effect demonstrates that electrons are only dislodged from a metal if incident light meets a minimum threshold frequency. I wonder if a varying intensity might also ...