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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2answers
111 views

Uncertainty principle in quantum field theory

Can the uncertainty principle be derived in quantum field theory? If yes, does is have a different interpretation than quantum mechanics because the coordinates $x_i$ are now parameters and not ...
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1answer
64 views

Time reversal in quantum mechanics

If the time reverse operator is defined as \begin{equation} \mbox{T}|\psi(t)\rangle=|\psi(-t)\rangle \end{equation} I am now considering time reversed $\hat x$ and $\hat p$ (of course in Heisenberg ...
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0answers
46 views

How to evaluate this odd path integral?

Is there any analytical solution on this path integral? \begin{align} &P(\theta_{N} t_{N}| \theta_{0} ...
4
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1answer
127 views

Why can't quantum field theory be quaternion instead of complex?

So, the definition of QFT in terms of path integrals is that the partition function is: $$Z[J] \propto \int e^{iS[\phi]+J.\phi} D[\phi]$$ But does it have any meaning if instead of this $U(1)$ ...
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1answer
85 views

Operators is a infinite dimensional matrix, how can it multiply by a wave function that is a n*1 (n is finite) matrix

My confusion started from thinking the quantum superposition principle. Several website say that the quantum superposition means all state can be represented as infinity superposition of orthogonal ...
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1answer
40 views

How to experimentally create an atom in a superposition of ground and excited states? [closed]

For Quantum Computing we use atoms in superposed states, but how do we physically create them?
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1answer
59 views

Any three-body Hamiltonian? [closed]

Is there an extension of spin interactions into three-body interactions such as $$H\sim \sum J \sigma_1\otimes \sigma_2 \otimes \sigma_3$$
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1answer
43 views

Analytical non-separable solution for schrodinger equation

I am an undergraduate with the background of a first course in Quantum Mechanics. I want to find out if there exist non-unique solutions to Schrodinger equation. So I have to find potentials ...
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1answer
32 views

“Independent simultaneous eigenbras” in Dirac's book 'Principles of Quantum Mechanics'

I've been puzzling through this book off and on and can usually work out what is going on via other external references on the Intertubes. But, this paragraph from pages 55 and 56 has me a bit ...
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1answer
31 views

What is the condition for local operations on bipartite entangled state?

I have an entangled state between Alice and Bob $|\psi\rangle_{AB}$ ( both Alice and Bob have states in Hiblert space of dimension $n$ ). Alice and Bob can only perform local meaurements. I assumed ...
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4answers
299 views

Heisenberg uncertainty principle clarification

I found these two examples in a books which demonstrate Heiseberg's uncertainty relation: 1) It shows that when we try to locate a moving electron,we transferred momentum via the photon that we ...
2
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0answers
46 views

Non-Linear O.D.E

I have reached a set of ODE as \begin{align} &\ddot{\vec{a}}(t)+\omega_0^2\frac{\cos{(b(t))}\sin{(a(t))}}{a(t)}\vec{a}(t)=0\\ &\ddot{b}(t)+\omega_0^2\cos{(a(t))}\sin{(b(t))}=0 \end{align} ...
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1answer
103 views

Physical implications of the Gibbs phenomenon for Quantum Mechanics

From Wikipedia: The Gibbs Phenomenon is the peculiar manner in which the Fourier series of a piecewise continuously differentiable periodic function behaves at a jump discontinuity. The nth ...
4
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2answers
83 views

Hamiltonian related to Riemann zeta function [closed]

using the eigenvstates of the Harmonic oscillator could we give a meaning to the Hamiltonian $$ H=\log(a.a^{+}+1) $$ here $ a$ and $ a^{+}$ are the creation/anihilation operators with commutation ...
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1answer
38 views

Information and entaglement via determination of the first's system state with interaction

Could we have entangled systems (microscopical or macroscopical) and construct a way of altering the state of one of the two entangled parts (let's say by Alice) via interaction and thus making the ...
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1answer
63 views

What is the recent most important discovery and study about magnets? [closed]

I believe that magnetism is a very powerful tool to do various things.It can make amazing machines.What is the recent most important piece of study that has been done of magnetism. The study that can ...
3
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1answer
118 views

Was quantum mechanics made to fit the Bell violations or they just happen to fit them?

Entangled bipartite states can violate the CHSH inequality upto $2\sqrt{2}$ with suitable measurements. Is it that in nature we don't witness violation of CHSH more than this and quantum mechanics ...
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2answers
94 views

Does the many worlds interpretation eliminate the spooky action at a distance paradox? [closed]

I'm sorry if this is a stupid question. I'm a novice at physics. I have read the article about entanglement and EPR paradox. The spin of two particles is measured when they are very far apart, and ...
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1answer
62 views

Phase on Aharonov-Bohm effect doubts

How I show that $$\Lambda(\textbf{x}')=\frac{q}{\hbar}\int \mathbf{A} \cdot d\mathbf{x'}$$ on $$ \tilde{\psi}(\textbf{x}',t)=e^{[\frac{iq\Lambda(\textbf{x}')}{\hbar c}]}\psi(\textbf{x}',t)$$ for ...
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2answers
123 views

Is this a sufficient condition for a state to be an eigenstate?

$\renewcommand{ket}[1]{|#1\rangle} \renewcommand{bra}[1]{\langle#1|} \renewcommand{braket}[2]{\langle#1|#2\rangle} \renewcommand{bbraket}[3]{\langle#1|#2|#3\rangle}$ I'm trying to wrap my head around ...
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1answer
70 views

Where do these two equalities for the expectation value come from precisely? Doesn't $\Psi^* x \Psi = x |\Psi|^2$?

Where do these two equalities for the expectation value come from precisely? : $$\begin{align} \langle x\rangle &= \int_{-\infty} ^\infty \Psi^* x \Psi\,\mathrm{d}x \\ \langle x^2\rangle &= ...
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1answer
60 views

The Tunnelling Man [closed]

What's the probability that I will tunnel through a solid wall? By "tunnel" I mean, the probability of finding me on the other side of the wall. Assumptions Wall thickness = $d$ Clearly state any ...
2
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0answers
38 views

Measuring quantum entanglement in paper by Ma et al [duplicate]

Looking at the links below, could somebody please explain how entanglement between Alice and Bob particles is established/deduced from Victor's choice/measurement? I understand that Alice and Bob can ...
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0answers
12 views

Application or Applicability Spin Seebeck Effect

I am looking for any application or study of applicability of the Spin Seebeck Effect. I have not found anything good anywhere so far but maybe someone here knows something? Would appriciate any ...
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1answer
55 views

Compton Scattering Feynman diagram integral expression

I'm trying to write down the integral expression according to the feynman-rules for this Diagram of an electron with compton scattering and a one-loop correction: ![Compton Scattering][1] ...
1
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1answer
110 views

Quantum mechanic particle

In non relativistic quantum mechanic, we are dealing with a problem involving a particle in one dimensional space, and it has been given the potential and it reads: ...
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2answers
96 views

Layman's explanation of the mysterious occurrence of quantum tunneling?

I see much talk about probability and functions, quantum states and ball-in-a-pit analogies. Bah. I would like an easy summary about the principles behind, demonstrations of, and application from ...
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1answer
146 views

How is quantization related to commutation? [duplicate]

How are commutation (of observables) and quantization related? Reading about the Stone-Von Neumann Theorem, it seems that commutativity is the classical limit of quantum mechanics, and hence ...
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1answer
42 views

Particle position and speed [duplicate]

If I understand correctly, particle is something at a point of time, where you can tell it's position, but what if particle is moving, then you can tell it's speed. From what I understand wave is NOT ...
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0answers
5 views

Verdet Constant and optical pumping

While studying Faraday rotation (linear magneto-optic rotation) I came across a fact that faraday rotation can be enhanced. Verdet constant which depends on the wavelength can be enhanced as change in ...
5
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2answers
119 views

Quantum entanglement and the big bang

Prior to the Big Bang all matter was compressed into a point of high density. Why isn't all matter already entangled?
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1answer
109 views

Are Feynman's Six Easy Lectures still relevant today?

I haven't learned anything about modern physics at the university yet, but next year I will, and in the summer before I thought I would read this book, Six easy lectures from Richard Feynman. It was ...
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0answers
31 views

Delayed choice entanglement swapping: why are Alice & Bob's measurements useless without Victor's?

Here is the article by Ma et al.:http://arxiv.org/abs/1203.4834 I have read many explanations on this site and others that emphasize that Victor's data is needed to make Alice and Bob's usable... ...
4
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1answer
71 views

Constructing differential equation from arbitrary Hamiltonian

Suppose I begin with the time-independent Schrodinger equation $$ \left(-\frac{1}{2m}\partial_x^2 + V(x)\right)\psi_n(x) = E_n\psi_n(x), $$ ordinarily we specify the function $V$ and then solve for a ...
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0answers
15 views

Creating an arbitrary state of the quantum simple harmonic oscillator [duplicate]

Suppose $\mathcal{B}=\{\lvert 0\rangle, \lvert 1\rangle, \lvert 2\rangle, ... \}$ is the energy eigen-basis of a quantum simple harmonic oscillator. I want to create the state \begin{equation} ...
1
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0answers
76 views

Creating an arbitrary state of the quantum simple harmonic oscillator

Suppose $\mathcal{B}=\{|0\rangle, |1\rangle, |2\rangle, ... \}$ is the energy eigen-basis of a quantum simple harmonic oscillator. I want to create the state \begin{equation} |\Psi\rangle = ...
2
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1answer
73 views

Why are photons bosonic?

I am studying the quantization of the electromagnetic field. My text quantizes by changing amplitudes to ladder operators, by putting in an action and by imposing bosonic commutation relations upon ...
2
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0answers
29 views

Current density defined by the scattering operator

I have a problem with the definition of the current density. In most literature it is defined as $j^\mu=\frac{i}{2}(S^*\frac{\partial S(A)}{\partial A_\mu(x)})$. I understand that normally we use ...
1
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1answer
114 views

What is quantum mysticism? [closed]

Most of my questions on stack physics exchange are being commented on as being quantum mystic. The questions I ask are basically related to device independence and how local hidden variable theory ...
0
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0answers
50 views

Which bipartite entangled states violate the CHSH maximally?

I am reading the device independent outlook on quantum mechanics. Here the author gives a proof that for two qubit system maximally entangled states violate the CHSH inequality maximally that is upto ...
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0answers
30 views

Analogy between a classical discrete system and non classical continous system

Most introduction textbooks about quantum fieldtheory start with a discrete classical harmonic oscillator and then looks at it in the continuous quantized case (quantized field). This leads to the ...
0
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1answer
70 views

Only get part of commutator form expanding to third order in generator expression

(Shankar 12.2.4) Let $U[R(\epsilon_z\hat k)] = I - {i\over\hbar}\epsilon_z L_z$ be the infinitesimal generator for rotation operators, and $T(\vec\epsilon) = I - {i\over\hbar}\vec\epsilon\cdot\vec ...
3
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2answers
121 views

Spin zero photons

As I understand it, the reason why there is no Spin 0 Photon is because the polarisation of an EM field lives in two dimension. Hence we only have two basis vectors, yielding two pairs of ladder ...
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0answers
32 views

Coherence theory and spatial/temporal coherence

I'm working on a beyond the Standard model (BSM) experiment (on its theoretical side, actually) and I really need to understand better the concepts of spatial and temporal coherence. The rough idea ...
1
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2answers
74 views

Larmor Precession - What does precession actually means?

Larmor Precession - What does precession actually means? Is it change in the orientation of the axis with which electron revolves around the orbit or what. But, shouldn't the radius of the orbit ...
0
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0answers
35 views

How to calculate the eigenenergies of a particle in a triangular billiard?

Suppose we take the Dirichlet boundary condition, namely the wave function must vanish on the boundary. How about a general n-polygon?
0
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1answer
15 views

Can we agitate a classical non viscous fluid?

Suppose we have an infinite amount of a non viscous liquid (No boundary). Inside that liquid works a rotating impeller. Can the impeller agitate the liquid at all? The question arise from thinking ...
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2answers
49 views

Dirac notation and column representation

$\renewcommand{ket}[1]{|#1\rangle}$ I am facing difficulty in understanding how the right hand side is coming in equation A below In $H$ of dimention 4, the vector $$ \sqrt{\frac{2}{3}} ...
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0answers
32 views

What determines the spatial variation in phase in a superconductor?

I'm assuming that since a superconductor is in one common wave function, the time evolution is governed by the typical global phase variation: $$ \psi (t) = e^{-\frac{i}{\hbar}E_nt}\psi(0) $$ ...
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3answers
141 views

Why is only one quantity of angular momentum i.e. $L_z$ quantized & not $L_x$ & $L_y$?

This is quoted from Arthur Beiser's Concepts of Modern Physics: Why is only one quantity of $\mathbf{L}$ quantized? The answer is related to the fact that $\mathbf{L}$ can never point in any ...