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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When you make materials smaller is there a trend in the manner light is absorbed or reflected?

For instance if you take gold is shines like yellow, but if you make it smaller I've heared that it absorbes more the smaller frequencies. At a size of 100nm a piece of gold will absorb fe more blue ...
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1answer
14 views

What is the correct statement of Kirchhoff's Law of Thermal Emission?

There are various quite different statements in textbooks and other science literature as to Kirchhoff's Law of Thermal Emission. So, what is the correct statement of Kirchhoff's Law of Thermal ...
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0answers
13 views

Loss of interference in single-photon Mach–Zehnder interferometer with detector in only one arm

I have read that if you have a Mach–Zehnder interferometer (doing a single-photon experiment) and put a detector in only one of the two arms (connected to the first beam splitter), you lose ...
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0answers
12 views

density of states with changing potential floor

I wish to calculate the density of states for a 1D finite potential well, for the scattering states, meaning $E>0$. I have a potential of the form: $$ V(x)=\begin{cases} -V_0 & |x|<a\\ 0 ...
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1answer
97 views

Help needed to understand “On the reality of the quantum state”

I am having trouble to understand the reasoning in the following paper, On the reality of the quantum state. MF Pusey, J Barret and T Rudolph. Nature Phys. 8, 475–478 (2012); arXiv:1111.3328. ...
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6answers
75 views

Is QM something that belongs to all relative small particles or only to subatomic particles?

For us human beings subatomic particles like elektrons are described by the laws of QM. But imagine their is a very huge giant looking on the universe. For him all the planets and stars are so tiny ...
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Are there some explication for the wave function in Quantum Mechanics? [on hold]

I start to learn the Quantum Mechanics and I don't really understand the mechanisme behind the wave function. As what I feel and as I think the world as multivers, 1/ I see wave function like a way ...
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37 views

Spinor on an eigenstate of $J_z$

The state of a particle with spin 1/2 is described (in the $S_z$ representation) by a spinor $[\Psi]=\left( \begin{array}{c} \phi_+ \\ \phi_- \\ \end{array} \right)$ Its known to be eigenstate of ...
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7answers
1k views

How can a product of Bra and Ket be a scalar if they are matrices?

I am trying to teach myself Quantum Mechanics and am currently on Complex Vector Space Arithmetic. According to Wikipedia, product of a Bra and Ket is a scalar (which, I think, means a complex ...
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1answer
41 views

What is the origin of the quantum operators for p and E?

It is always stated the quantum operators for p en E are the ones we´re familiair with. But where do these operators come from?
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46 views

What would be the research advances if we discover the gravitational waves? [on hold]

As researchers of LIGO (USA) and VIRGO (France/Italy) say that they have discovered gravitational waves thanks to black hole collision today, what would be, apart of the important confirmation of ...
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40 views

Physical meaning of weight function in inner product in Quantum Mechanics

When taking the inner product of say two functions in Quantum Mechanics,we include a weight function w(x,y,z) that is usually equal to unity(in my undergraduate introductory QM course anyway). But ...
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0answers
21 views

Restriction to the total angular momentum of two identical particles with spin 1

I've been asked if there is any aditional restriction to obtain the possible values of the total angular momentum J by considering that the 2 particles of spin S=1 are identical. If they are not ...
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0answers
32 views

Proving Probability Current and Momentum relationship

I am trying to show that $\mathbf j = \frac{\hbar}{2mi}\left(\Psi^* \mathbf \nabla \Psi - \Psi \mathbf \nabla \Psi^{*} \right) \,, $ simplifies to $\mathbf j = \frac{\mathbf p}{2m} (|\Psi|^2) $. I ...
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0answers
28 views

In what circumstances, can exchange interaction acquire temperature dependence?

Heisenberg exchange interaction (sometimes called as magnetic stiffness?), originating from the Coulomb interaction and the Fermion statistics, is widely used in theories of magnetism. Conventionally, ...
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0answers
18 views

What frequencies is radation being emited in infinite potential well

The problem that I am working on is. Consider an electron in an infinitely deep one-dimensional potential well of width 1nm . This electron is prepared in a state that is an equal linear ...
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2answers
99 views

What is the opposite of quantization?

Is the opposite of quantization just taking the limit $h \rightarrow 0$ ? Or are there more steps involved (maybe related to bosons and fermions?)? How would one call the the opposite of quantization? ...
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1answer
124 views

Do I need to consider the spin of electrons when they are in infinite potential well

This is the problem I have And this is one of my books tell me what should I do And my question is: Do I need to consider spin in this case?(that is, I don't think the book is right...) I found ...
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0answers
33 views

Normalizing ket vectors

So I've run in to a bit of a notation problem on my coursework I have a vector, |A> expressed in the orthogonal basis |1> and |2> |A> = |1> + i |2> I need to convert it into bra form to normalize ...
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34 views

De-broglie wavelength [on hold]

The de-broglie wavelength of an electron emitted from the ground state of an H-atom after the absorption of a photon equals 1/2 of the de-broglie wavelength when it is in orbit. The energy of the ...
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2answers
49 views

Is the video “How to Reveal Subatomic Particles at Home”'s explanation of its experiment misleading?

https://www.youtube.com/watch?v=wN_DMMQEhfQ The video asserts that along the path of an electron or muon, a trail of condensation will appear. But from what I understand, if an electron or muon (both ...
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0answers
51 views

Undergraduate Physics Senior Research Topic (Theory/Mathematical Physics Based) [on hold]

This is most likely a question for those who have experience/knowledge of theoretical/mathematical physics at the graduate level and can provide recommendations following my criteria. Here is some ...
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0answers
23 views

ferromagnetic and Curie temperature. Energy question

Is energy absorb and release back when a ferromagnetic material heats and cools passing through the Curie temperature?
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1answer
100 views

How can space and time occur spontaneously? [on hold]

In the book: "A universe from nothing" by the theoretical physicist Lawrence Krauss he mentions that space and time can occur spontaneously. Unfortunately he does not explain how. So my question is, ...
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51 views

On the Pauli Principle

Consider a quantum mechanical system as shown-say a piece of metallic conductor in the shape of a long, thin bar.(Must it be a single crystal to be considered a "system"?). Now focus on two free ...
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0answers
27 views

Does a set of eigenvalues in QM correspond to a random variable in statistics? [duplicate]

In quantum mechanics the possible outcomes of a measurement of a quantity corresponding to a linear hermitian operator $A$ are only the eigenvalues $a_i$ of $A$ (see e.g. ...
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38 views

Decoherence and interpretations

With quantum decoherence, are there still any "gaps" in our knowledge of quantum mechanics that hint (either in terms of the physics, philosophy, or otherwise) at the need for further interpretation? ...
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1answer
35 views

Orbital angular momentum eigenstates in the $|\mathbf{r}\rangle$ representation

Consider the orbital angular momentum operators $L^2$ and $L_z$. In the $|\mathbf{r}\rangle$ representation using spherical coordinates those operators actions are given by ...
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0answers
18 views

P-N Junction - (Depletion Region) [duplicate]

Will i have simple q ,,, Why the electron in N Type don't go to the Formed Positive Ions ?
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0answers
39 views

Entanglement in laser beams [on hold]

Recent experiments in entanglement of two laser beams using OPOs indicates higher level of entanglement. But laser beams are nothing more than group of photons. How are the photons inside the two ...
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0answers
23 views

Measurement without collapse

Does anybody have a reference for Cini's model of Quantum Measurement theory. I have a background of Quantum Mechanics (Ballentine level). Also I don't have access to Cini's paper.
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0answers
20 views

To which extent is the treatment of nuclear multipole radiation by the means of a classical electromagnetic field valid?

In the treatment of nuclear multipole radiation, for example in the context of nuclear gamma decay, it is standard, at least at the elementary level, to formalize the electromagnetic radiation as a ...
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1answer
31 views

Is the relation c=νλ valid only for Electromagnetic waves?

What is the validity of the relation $c = \nu\lambda$? More specifically, is this equation valid only for Electromagnetic waves? I read this statement in a book, which says: de Broglie waves are ...
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17 views

Simple Harmonic Osillator [on hold]

For simple harmonic oscillator, calculate a. The energy b. The mean position c. The mean momentum square d. Standard deviation of position e. Standard deviation of momentum f. Cheek uncertainty ...
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0answers
18 views

flux quantization in quantum hall effect

Why is it that in the quantum Hall effect (integer or fractional) the number of flux quanta penetrating the surface is integer? I can see how the flux quantum arises if you calculate the degeneracy of ...
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22 views

Angular Momentum Addition in Phase Space QM

In my very limited understanding of geometric quantization, we quantize spin by choosing as our phase space $S^2$ with a suitably normalized area form as the symplectic form. Depending on the ...
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1answer
35 views

Scattering amplitude Green's function integral

On page 208 of Weinberg's QM book, he calculates the following integral \begin{align} G_k (\vec{x}-\vec{y}) =& \int \frac{d^3 q}{(2\pi \hbar)^3} \frac{e^{i\vec{q} \cdot (\vec{x}-\vec{y})}} ...
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1answer
51 views

Time Dilation and the direct opposite [on hold]

// I just looked this up in google 30 kilometers per second Thus, the surface of the earth at the equator moves at a speed of 460 meters per second--or roughly 1,000 miles per hour. As ...
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1answer
57 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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0answers
31 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
19 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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4answers
60 views

Can we obtain interference pattern with single electron/photon in Young's double slit experiment? [duplicate]

Can we obtain interference pattern by using single electron/photon in Young's Double slit experiment? If yes, then how ...and if no, then why?
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0answers
27 views

measurement of tripartit qubit state [on hold]

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
188 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
81 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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0answers
23 views

local unitary transformation [on hold]

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
67 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
118 views

Quantum entanglement - problem with Bell's inequality [on hold]

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
58 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
36 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 ...