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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7 views

Photograph of Light as Wave and Particle

what is this? actually its the first photo of light as wave and a particle. The bottom "slice" of the image shows the particles, while the top image shows light as a wave. i have questions 1.how ...
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4answers
52 views

Why does moving electron emits photons?

I have read that moving or oscillating electron emits photons. But why and how does it so? And why only photons? There are other bosons like gluons, W and Z bosons, so why does electron emit only ...
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0answers
11 views

Electron confinement energy

I was introduced the electron confinement energy. At room temperature thermal energy of a particle is about $k_B T$, where $T=298K$, giving about $25meV$. I was told that $E_{confinement}=50emV$, ...
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2answers
31 views

'schrodinger' picture in measurement based topological quantum computation

I am looking at the measurement processes in topological quantum computation (TQC) as mentioned here http://arxiv.org/abs/1210.7929 and in other measurement based TQC papers. Let's say I start with ...
3
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3answers
87 views

Physical reason why the derivative of a wavefunction has to be continuous?

Question What is the physical reason (i.e. without any maths) that the derivative of a wavefunction (except with infinite potentials) has to be continuous? Other info I know that in the classical ...
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1answer
68 views

What really is a particle?

In Classical Mechanics we consider particles as things whose internal structure for the purpose of studying some phenomenon might be neglected. In that setting we associate particles to points and ...
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1answer
49 views

How might I show that an operator is, by definition, an 'observable'? [on hold]

Here is my problem: I understand what is meant by 'observable' but don't have a formal definition at hand. How do I 'show' it?
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0answers
27 views

Posibility of time travel/multiple realities/time phase shifting [on hold]

Sounds odd and unlikely, but let me explain the situation. Going on the de ja vue ideal, which we probably have all experienced, I believe things of such a matter are possible. Just today when I ...
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0answers
38 views

Getting to spins of arbitrary direction

Let me rephrase this question: Let us assume we know that symmetry transformations always look like this: $$U(s)=e^{iKs} $$ with a hermitian Operator K. This tells us that for very small $s$: ...
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4answers
137 views

Does quantum mechanics imply that particles have no trajectories?

In Classical Mechanics we describe the evolution of a particle giving its trajectory. This is quite natural because it seems a particle must be somewhere and must have some state of motion. In Quantum ...
1
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0answers
32 views

What is the relationship between coherent states and quantum coherence?

What is the relationship between coherent states and quantum coherence? To me coherent states were only talked about in regard to Quantum Harmonic Oscillator, whereas coherence and decoherence on the ...
2
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1answer
45 views

Number of Nodes in energy eigenstates

I have a question from the very basics of Quantum Mechanics.Given this theorem: For the discrete bound-state spectrum of a one-dimensional potential let the allowed energies be $E_1<E_2< ...
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0answers
28 views

Why we compare expectations sometimes and sometimes probabilities?

I am reading device independent approach on quantum mechanics from here device independent outlook on quantum mechanics. In here the author introduces local variable theory. Then he give two results. ...
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0answers
35 views

Scattering amplitude, link between quantum mechanics and QFT

In quantum mechanics, we can define the scattering amplitude $f_k(\theta)$ for two particles as the magnitude of an outgoing spherical wave. More precisely, the asymptotic behaviour (when ...
2
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2answers
111 views

Why does the magnitude squared of the wave function give us the probability density? [duplicate]

My question doesn't go much beyond the title: Why does $$\left | \psi \left ( x,t \right ) \right |^{2}$$ give us the probability density of something appearing at a certain location? I understand ...
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2answers
29 views

A binary operator required for observing whether the particle is present in a given spatial region

Consider the wave function $\psi(x)$, I want to define an experiment using quantum mechanical rules. The experiment is to find whether the particle is in the region of space (a,b). The observable is ...
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0answers
48 views

Difference in partition function of classical and quantum Ideal gas

First, I have read this question:What is meant by the term "single particle state" There is an analysis going on in my book (Mandle F. Statistical Physics) that has brought me in a ...
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0answers
56 views

Does EPR permit information to travel faster than light? [duplicate]

This question always throws me: Discuss if the EPR paradox violates special relativity? The information of the state of one particle is instantaneously transmitted to the other particle, but ...
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0answers
17 views

Hadron Annihilation - what happens with the constituents

When a Hadron and its antimatter equivalent annihilate, what happens to the QCD "soup" (for lack of an appropriate term) from each? Eg, the valence quarks in a proton - antiproton event, to they pair ...
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0answers
18 views

symmetry group of multi-electron atom

Neglecting spin effects, the energy levels of multi-electron atoms are characterized by states of definite total orbital ($L^2$) and spin angular momentum ($S^2$). From this it seems that the ...
6
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2answers
107 views

Do bras and kets have dimensions?

I'm trying to understand more intuitively what bras and kets are, but some aspects of them remain a mystery to me. We usually think of $\psi (x)$ as having dimension of $[1/\sqrt{L}]$ so that ...
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2answers
72 views

Have two identical quantum mechanical experiments ever been done?

Have two experiments ever been done such that the set up is identically the same, (when I say identically I mean down to the atomic level). Of course the experiment would have to be very simple. If it ...
2
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3answers
91 views

What can change a photon's frequency?

I found this question: Is it possible to apply force to a light particle? As it states, gravity can change the frequency of light by changing its momentum. My question regards other phenomena that ...
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1answer
47 views

Can someone explain what's the difference between all these terms in “Simple Words” with their “applications”? [on hold]

I'm very confused between all these terms. Can someone explain what's the difference between Classical Mechanics, Relativistic Mechanics, Quantum Mechanics, Quantum Field Theory, ...
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0answers
40 views

How is a measurement on an electron done?

There are two ways how to change a direction of a qubit - one with Larmor precession, another with a measurement. I am not sure about the measurement one. Let's say I have an electron with spin ...
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0answers
15 views

Infinite bare quantities and dressed quantities confusion

I'm getting very confused. Taking the example of the mass of the Z-boson. Constructing the GWS model using gauge symmetry breaking one finds a lagrangian which is a function of the Z-boson mass: ...
1
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1answer
46 views

Example for System Given Hilbert Space

What are some concrete examples of physical systems such that their corresponding Hilbert space is given by $\mathbb{C}$? Also, what is the physical difference between a system whose corresponding ...
1
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1answer
40 views

Uncertainty relation and instrumental errors

I was puzzled recently by what I've read in the internets about Heisenberg's uncertainty principle (one probably should never do this). It claimed that in the usual relation $$ ...
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1answer
41 views

Oberving a photon through double slits

If we send a particle with mass through the double slits we observe a interference pattern. That is of course if we don't observe which slit the particle goes through. If we do then we get two peaks ...
1
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1answer
17 views

Franck-Hertz experiment what transition takes place?

For the Franck-Hertz experiment there is a voltage drop at $4.9\rm\,V$. What transition does this represent in the mercury? Looking at the energy levels it seems to be from the ground to the 2nd ...
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1answer
31 views

Quantization in Black Body Radiation [duplicate]

Why does energy need to be quantized to explain black body radiation? Wouldn't the approximate normal distribution of the kinetic energy of particles at a certain temperature be sufficient, ie. few ...
1
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0answers
48 views

What's the advantage of using bra-ket notation over inner-product notation? [migrated]

Both notations look pretty similar, and appear similar when undergo algebraic operations. Apart from personal taste (aesthetics) concerning commas (<,>) vs. pipes (<|>), what is (are) the ...
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2answers
46 views

derivation qm canonical ensemble

In classical mechanics the canonical ensemble can be derived from the microcanonical ensemble of two systems in weak interaction. Is a similar thing possible in quantum mechanics? Is there any good ...
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2answers
80 views

How does this youtube video demonstrate quantum entanglement? [on hold]

The following is an experiment that shows "spooky action at a distance" of quantum entanglement; that is, when we measure some properties of two entangled photons, we find that measuring property of ...
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1answer
67 views

Books on quantum mechanics with intuition [duplicate]

So, I know that there are a lot of questions about good books on quantum mechanics and I have read each one of them, and I go on and bought Griffiths' Introduction to Quantum Mechanics. But the fact ...
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1answer
36 views

Density of states of 3D harmonic oscillator

for the first red box, shouldn't be $\epsilon^2 =\epsilon_{n_x}^2 +\epsilon_{n_y}^2 + \epsilon_{n_z}^2 + 2\epsilon_{n_x}\epsilon_{n_y} + 2 \epsilon_{n_x}\epsilon_{n_z} + ...
1
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0answers
46 views

Quantum mechanics not in $L_2$-space [duplicate]

As far as I understand the postulates of quantum mechanics use only properties of abstract Hilbert space. So could we use any other Hilbert space for calculations instead of $L_2$? What could it be? ...
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1answer
26 views

can we see or accumulate antiparticles

I would like to know if we can see antiparticles with our bare eyes instead of a technological detector. I realize we cant see individual atoms or particles but enough photons grouped together, for ...
2
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1answer
36 views

Long distance entanglement maintenance for quantum teleportation

Quantum teleportation starts out with an EPR pair being distributed among Alice and Bob i.e. one qubit goes to Alice and the other goes to Bob. The problem that I see in this scenario is the state of ...
0
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1answer
104 views

Doesn't Schrodinger's Cat depend on whether there's a quantum/classical boundary?

Everyone knows how Schrodinger's Cat is set up, so the question becomes whether there's a quantum/classical boundary and what that boundary is. Some people say everything is quantum while some may ...
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1answer
22 views

Adjoints in occupation number representation

I am having some trouble understanding how to compute things in occupation number representation. I believe my problem is only implicitly dealt with in the notes I have read. A simple example should ...
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0answers
212 views

Emdrive in relation to newest NASA article - Does it extract energy out of the QM vacuum? [closed]

related to this newest article by NASA concerning the EMdrive http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/ Such a vehicle would be capable of carrying two to six ...
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2answers
51 views

Why is a transmon a charge qubit?

The classic charge qubit is the cooper pair box which is a capacitor in series with a Josephson junction. In my understanding, by changing the gate voltage at the capacitor, one can create a ...
4
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3answers
96 views

Diffraction of matter waves

By considering the De Broglie wavelength of particles, we discover that matter can diffract if passed through openings with itself. This poses a variety of questions, namely Can matter waves ...
1
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3answers
80 views

Negative energy of free particle: classical and quantum picture

Classically, the energy of a free particle consists of only the kinetic energy given by $E=\frac{|\textbf{p}|^2}{2m}$ Since $|\textbf{p}| $is real and $m>0$, $E\geq 0$. However, since ...
3
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1answer
69 views

which are the non-abelian anyons for universal quantum computation

I am trying to get a list of non-abelian anyons that can be used for universal quantum computation by implementing gates via braiding. I found that Majorana fermions and para-fermions (not sure about ...
0
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1answer
38 views

Quantum probability of entangled spin-1/2 particles?

Let us say that you have two entangled spin-1/2 particles (entangled in such a away that angular momentum is conserved). Let us say particle 1 moves to the left and particle 2 to the right. We measure ...
0
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3answers
106 views

How exactly does wave theory of light fail to explain blackbody radiation? [duplicate]

I don't really understand the reason why wave theory of light fails to explain the blackbody radiation. My textbook says the Planck's quantum theory explains blackbody radiation. It says "If we ...
1
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1answer
52 views

Uncertainty principle within a neutron star or black hole

Take the time-energy uncertainty relation, $\Delta$$E$$\Delta$$T$$\ge$$\hbar/2$. My question is based on my confusion about the effect this relation may have within the interior of a highly ...
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0answers
25 views

Phase added on reflection at a beam splitter?

If we have light of a particular phase that is indecent on a beam splitter, I assume the transmitted beam undergo's no phase change. But I thought that the reflected beam would undergo a phase change ...