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 quantum-field-...

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What's the chance that two atoms would swap electrons?

Suppose two atoms are falling away from each other with velocity $v$ each. Suppose they have evenly distributed momentum among their electrons. Suppose one atom swaps an electron with the other atom. ...
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0answers
77 views

How does the wave function change upon a boost? [on hold]

I was recently thinking about Lorentz invariance description of a particle. In special relativity is based on the invariance of $$ \text{constant} = c^2t^2 - x^2 - y^2 - z^2$$ I was wondering if ...
3
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3answers
69 views

Does electron absorb energy?

According to my teacher, an electron is point sized and it does not absorb or release energy. Moreover, my teacher says their orbital absorbs energy rather than the electron. If that is the case, then ...
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3answers
588 views

Quantum Mechanics in Electric Field

I am working on a problem which looks like this. Consider a charged particle with charge $q$ trapped in a box of length $L$ with finite constant potential $ V_0 $ on both ends. A constant (static) ...
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3answers
93 views

Finding the Expectation value of harmonic oscillator

What is the expectation value for $e^{{\alpha}a^{\dagger}}e^{-\alpha^*{a}}$ of any two states of harmonic oscillator (let say $|n\rangle$ and $|m\rangle$) given below, $$\langle n|e^{{\alpha}a^{\...
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25 views

Existence of effective Hamiltonian for variational ansatz

I recently saw on Wikipedia that in perturbation theory one can define in a systematic way effective Hamiltonian $\hat{H}_{\rm eff}$ that produces the same kind of states and energies as if one ...
2
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0answers
41 views

Calculating the ground state energy in an electron gas (Jellium)

$\renewcommand{\phi}{\varphi} \newcommand{\vec}[1]{\textbf{#1}}$ This is pretty lengthy because I kept having ideas while writing this. Consider an electron gas in a cube of side length $L$, $V=L^...
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0answers
22 views

A fundamental theory of superunification [on hold]

So, an year ago I was searching over the Internet about anti gravity (just out of curiosity).. And I stumbled upon this article: http://theoryofsuperunification-leonov.blogspot.bg/2015/01/russia-...
14
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1answer
1k views

What are the odds of finding an electron a long way from an atom? As in metres away? [on hold]

Pretty self-explanatory, heard that there is a chance that you might find an electron on the other side of the universe, just wanted to know.
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1answer
48 views

Universe spawned from the death of a hyper black hole?

Some Cosmologists have speculated that the Universe formed from the debris ejected when a four-dimensional star collapsed into a black hole a scenario that would help to explain why the cosmos seems ...
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2answers
59 views

Can the Copenhagen interpretation and the many-worlds theory be somehow reconciled? [on hold]

Is it possible that, at the moment of observation, a timeline is created where an object is in a state which contrasts its state in the current timeline? Using Schrodinger's cat as an example, let's ...
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0answers
37 views

Where I can find quantum entanglement, real experimental raw data

For analysis purpose, I am looking for raw data from real entanglement experiment with spin measured at two detectors, at various combinations of angles, but preferably at a single combination of ...
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2answers
70 views

If orbital shells are just probability functions, why are quantum numbers only ever integers? [on hold]

Quantum numbers are supposed to denote every individual orbital. But if orbital shells are probability functions, then orbitals can't be definite, solid things. So in that case, there can be variation ...
1
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1answer
180 views

Expectation value of total angular momentum $\langle J \rangle$

[I am working with Griffiths Introduction to Quantum Mechanics, 3rd Edition. My problem is general but if you want to look I am reading from ch 4.1 in which the weak-field Zeeman Effect is being ...
3
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2answers
48 views

Meaning of “Metrically defined” matrix

I got stuck on understanding stuff from Methods of molecular quantum mechanics written by R. McWeeny. The content is: It must be stressed that the representation property embodied in $\mathcal{A} \...
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0answers
90 views
+50

Zeno effect in quantum gravity?

Given that "the quantum zeno effect can "freeze" the evolution of the system by measuring it frequently enough in its known initial state." Is there any equivalent/similar Zeno effect in quantum ...
2
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0answers
30 views

Quantum Entanglement Simulation

Suppose there is a digital "quantum entanglement simulator" with a pair generator and two spin detectors, and it Allows to create as many pairs as you want (100 pairs per single click) Allows to ...
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1answer
44 views

What happens with QM particle at constant velocity? [on hold]

In QM particles have wavefunctions that disperse quite fast. The FWHM for gaussian wavepacket increases in time as $\Delta x(t)= \Delta x_0\sqrt{1+(t/\tau)^2} $, $\tau=2m(\Delta x_0)^2/\hbar$ What ...
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2answers
100 views

What is the program of quantum field theory? What is its derivation?

Paraphrasing Griffith's: For some particle of mass m constrained to the x-axis subject to some force $F(x,t)=-∂V/∂x$, the program of classical mechanics is to determine the particle's position at any ...
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1answer
85 views

How to use Heisenberg to explain atom cannot be at rest

In a Dutch national physics exam at the level just before entering university there was a question about a molecule HI: one atom hydrogen plus one atom iodine. Within the molecule, the hydrogen ...
2
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2answers
396 views

'The size of an atom' using Uncertainty Principle

Suppose we have a hydrogen atom, and measure the position of the electron; we must not be able to predict exactly where the electron will be, or the momentum spread will then turn out to be infinite. ...
0
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1answer
64 views

Approximation of an integral for time dependent quantum Hamiltonian

I want to approximate $\displaystyle\int_{t}^{t+h} dt' H(t')$ in its taylor series, $$H(t)h + \frac{1}{2}\frac{dH(t)}{dt} h^2 + \frac{1}{3!}\frac{d^2H(t)}{dt^2} h^3 + \frac{1}{4!}\frac{d^3H(t)}{dt^3} ...
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53 views

What's the intuition behind the Choi-Jamiolkowski isomorphism?

What is the intuition behind the Choi-Jamiolkowski isomorphism? It says that with every superoperator $\mathbb{E}$ we can associate a state given by a density matrix $$ J(\mathbb{E}) = (\mathbb{E} \...
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1answer
52 views

Quantum entanglement of spins

Suppose we have a pair of spins in the state $\left|\Psi\right>=\frac{1}{\sqrt2}(\left|\uparrow\downarrow\right>-\left|\downarrow\uparrow\right>)$. We know that the measurements of the spins ...
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2answers
59 views

How do Rabi oscillations act on the relative phase of state kets

Suppose we have a system with a lower state $\left|{\downarrow}\right\rangle$ and and upper state $\left|{\uparrow}\right\rangle$, coupled by a pulsed electromagnetic field. I thought that from an ...
2
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1answer
31 views

Switching Parity in a Superconductor

I've got a pretty simple question that's been bothering me for a while. This is the issue. Suppose we have a superconductor with phase $\phi$, and we change this to $\phi+2\pi$. One would think that ...
2
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1answer
60 views

Proper definition of the Wannier function

I am studying the construction of the Wannier functions for 1D system with periodic boundary conditions and my reasoning seems to be a little bit different from what I can find in textbooks. First ...
5
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1answer
74 views

Energy Spectrum and Gauge Transformations

There is a question in SE about the fact that the Hamiltonian isn't invariant under the EM gauge transformations. I wanted to ask about its consequences here. I know that in general, the Hamiltonian ...
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1answer
129 views

Question regarding NaCl equilibrium separation

So I am tutoring someone later and one of the problems is from Eisberg/Resnick Ch 12. The potential energy $V$ of NaCl can be described emperically by $$V = \frac{-e^2}{4\pi\epsilon_0 R}+Ae^{-R/\...
0
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1answer
23 views

What is the maximum limit for concurrence for a multiparticle state derived from a symmetric hamiltonian? [on hold]

What is the limit for the Entanglement of a multi particle state? Say I have N spins and a symmetric Hamiltonian. Is it 1 or more? Is there a limit at all? I thought it would be 1, since that value ...
3
votes
2answers
199 views

Rigorous Mathematical Proof of the Uncertainty Principle from First Principles [duplicate]

While looking at an intuitive explanation for the Heisenberg Uncertainty Principle (related question below), there was a mention of an axiomatic approach to establishing the uncertainty principle. ...
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20 views

Quantum Confinement in Quantum Dots

I have seen it referenced in several places that an electron will behave classically in a bulk material but as the dimension of the material in which the electron exists is limited below the electron'...
5
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1answer
68 views

Which charge to use in the Dirac quantization condition?

I have a follow-up question to Dirac magnetic monopoles and quark fractional electric charge quantization, regarding whether the "unit of electric charge" in the Dirac quantization condition should be ...
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3answers
2k views

What is a completely positive map *physically*?

I am sure this question is really stupid, but I could not refrain from asking it in this forum. This can be considered as a continuation of this question. ...
2
votes
1answer
141 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 ...
2
votes
1answer
66 views

Is the use of term Measurement appropriate in quantum physics

It may not sound like a physics question, but I think, it is. When we measure spin of an electron in a certain direction, we are actually, setting it up in that direction. That does not sound like ...
4
votes
2answers
633 views

Can 3 photons be combined to give a spin-0 projection?

Motivation: The neutral pion decays to 2 photons ($\pi^0\to\gamma\gamma$) most of the time. For the decay of the neutral to 3 photons ($\pi^0\to 3\gamma$) we have an upper limit on the branching ...
2
votes
2answers
67 views

Express state as eigenkets

This is very basic but I just suddenly got confused. Any state can be expressed as complete set of eigenkets with discrete eigenvalues: $$|P\rangle = \sum^n c_n |p_n\rangle$$ I understand the above. ...
2
votes
1answer
56 views

Relationship between position and momentum matrix elements

I am going through Faist's Quantum Cascade Lasers book. In the first section of the fourth chapter, he asserts that (in the context of a perturbative analysis of electronic transitions) the ...
3
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1answer
49 views

How to make a double slit electron interference as a home experiment? [on hold]

I want to see electron interference making my own experimental equipments. Do you think it is possible? Especially, double slit, how can I have it?
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0answers
34 views

Why can the y and z-components of spin be measured simultaneously? [duplicate]

I have a gut feeling that this is wrong. By the uncertainty principle where $x,y,z$ are the $x,y,z$ components of spin $$ \sigma_{y}\sigma_{z}\geq \frac{\hbar}{2}\langle x \rangle $$ and it can be ...
1
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0answers
35 views

Are all kinds of energy quantized? [duplicate]

I was reading this answer of David Z about meaning of "Quantum" that this question came in mind: If light is quantized (i.e. is a integer multiples of some unit $\hbar c/k$), are other kinds of ...
0
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2answers
204 views

Why only 1 component of angular momentum?

Griffiths says that you can have only 1 well defined component of the angular momentum because of the uncertainty principle. From the uncertainty principle, we get that $$ \sigma_{L_x}\sigma_{L_y} \...
-2
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0answers
33 views

Coordinate determines the speed and thus coordinate [on hold]

I have a question about configuration space. You say that coordinate and momentum have one-to-one correspondence in Quantum Mechanics. Imagine that coordinate of a particle is known absolutely in ...
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0answers
69 views

Why isn't CPU made of cesium 133? [on hold]

If this atom can move there and back 9 bilion times per second, then why are we using so poor CPUs?
9
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1answer
641 views

Confusion in a trick in solving an energy eigenfunction

Given a non-relativistic energy eigenfunction for a central potential $\left|\Phi \right>$ In solving relativistic hydrogen atom, one of the terms is $$ \left<\Phi\middle|\frac{e^2}{r}\middle|\...
0
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1answer
51 views

What is the process of a photon transforming into an electron and positron? [duplicate]

How did they come into existence from a photon? Is it really understood how the process works? Is there even a process or is it just something fundamental?
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0answers
72 views

Why is gravity viewed as a force? [on hold]

Before I say my thoughts on this I wanted to state that most of my knowledge on physics and such is from college books, and not from actual instruction. From my understanding of forces, there must be ...
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0answers
49 views

Does “Schroedinger's cat” need entity knowledge to work? [on hold]

I've never studied physics, but am interested in whether this paradox, from an interpretation of quantum mechanics, can still be stated if we don't know anything about unobservable entities. My ...
3
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1answer
110 views

On a measurement level, is quantum mechanics a deterministic theory or a probability theory?

Quantum mechanics is a non-commutative probability theory. As such, it fundamentally behaves differently from classical probability theories. This manifests itself most pronouncedly in the uncertainty ...