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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24 views

History of delta barrier in QM [migrated]

I'm interested in finding something out about the history of the problem of the delta potential barrier in QM. Which was the first study to propose this problem, and perhaps any particular motivation ...
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34 views

Elitzur–Vaidman bomb tester value on Wikipedia

Looking at this diagram from Wikipedia: I was trying to make sense of the sentence the interference is constructive at C and destructive at D Let's take a look at the superposition at C. ...
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46 views

The propagator method versus Schrodinger time dependent equation [closed]

What advantage does the the propagator, $K(x,t; x',t')$, method has over the solution of Schrodinger time dependent equation (STDE) for example in harmonic ocillator problems? I don't see any. See ...
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4answers
102 views

Physical intuition behind negative values for wave function?

So a positive and a positive wave function create a bonding orbital where the probability of finding an electron is summed while a positive and a negative create an anti-bonding orbital with a lower ...
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1answer
57 views

Performing the two slit experiment under a strong gravitational force

For elementary particles, are their associated De Broglie wavelengths affected by the spacetime curvature produced by large mass density values? I ask this as a newcomer to Q.M. so apologies if I ...
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2answers
85 views

Thought experiment on light accumulation

Consider an object which is a spherical one-way mirror, and let's call it the "Sphere". For the needs of the thought experiment, suppose that: the Sphere is perfectly spherical the mirror is ...
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1answer
39 views

How to form the spin triplet - singlet states from two electrons with spin not an eigenstate of $ S_z $ (spins not along z-axis))

For a two electron system, we know that the total $ J^2 $ states (Triplet - Singlet) are related with the $\uparrow \downarrow $ , $\downarrow \uparrow$ , $\uparrow \uparrow$ , $\downarrow \downarrow ...
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1answer
54 views

Why was the Stark effect discovered much later than the Zeeman effect?

This is strange. The Zeeman effect involves the magnetic field. The Stark effect involves the electric field. In the course of classical electrodynamics, we get the impression that for many physical ...
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62 views

Definition of Hamilton operator

The Hamilton operator is by definition a self-adjoint operator $H\text{: }D\left(H\right)\to\mathcal{H}$ with $D\left(H\right)\subset\mathcal{H}$ a dense linear subspace of the Hilbert space ...
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1answer
26 views

Proton spin independent fine structure “Hamiltonian” $W_f$

To find the perturbation correction (fine structure) in the case of a degenerate energy $E_n^0$, we can diagonalize the operator $W_f^n$, the restriction of $W_f$ to the eigen-space associated to ...
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3answers
82 views

Does the ratio of thermal energy to planck's constant have physical significance?

I realized that I had never noticed that $\left[ \frac{\hbar}{k_B T} \right]=$ Time. At $T \approx 300 K$, we have $\frac{\hbar}{k_B T} \approx 10$ fs. What, if anything, does this quantity mean? Does ...
2
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1answer
73 views

Physical meaning of wavelength of an EM wave

What is the physical meaning of the wavelength of light? This question has been asked before but I cannot find a satisfactory answer. Some respondents have said that the question is vague, I don't ...
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33 views

A real 'two line' (non-interference pattern) when observed

I have seen many interference patterns from double slit experiments but I have never seen a real 'two line' pattern when observed. Does this actually exist or is it only a conclusion? if there is an ...
2
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2answers
71 views

How can we know that all of the results for entangled photons are not chosen when the pair is created? [duplicate]

I was reading this introduction to quantum computing that says that when one photon in a pair of entangled photon is measured, the other one will have the opposite result when measured in the same ...
2
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0answers
49 views

What's actually going on when light interacts with matter?

There are many different theories but all of them fail to explain all 3 phenomena of light(absorption,emission,transmission). https://www.youtube.com/watch?v=CiHN0ZWE5bk ...
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1answer
70 views

Is the photon's wave function the same as an electromagnetic wave(light)? [duplicate]

The first that i have been taught in Quantum Mechanics is the photoelectric phenomenon. Without analyzing it, it concludes that when we shine light at the circuit(roughly speaking), the work required ...
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3answers
53 views

Is the perturbation Hamiltonian an observable?

In fine structure calculation we use the perturbation theory. The basic Hamiltonian $H_0$ is perturbed as: $H = H_0 + W$ First, the basic problem assume that $H_0$ is an observable. That allows to ...
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1answer
40 views

$L_y$ in terms of $L_+$ and $L_-$? [closed]

On the 5th slide of http://web.ift.uib.no/~lipniack/phys201_v08/angularmomentum.pdf, they say that: $$L_y=\frac{i}{2}(L_+-L-)$$ And this is not the only place I have seen this ...
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1answer
67 views

spin independent observable

Let's consider a spin independent observable $O$ (the terms of the operator don't depend upon the spin operator). If we are interested to find an eigenfunctions' basis of the wave-functions' space, ...
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2answers
114 views

Function of observables in mathematical words

In mathematical words, an observable is an operator that a set of linearly independent eigenfunctions constitutes a complete basis of the wave-functions' space. Now, let's consider some observables: ...
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1answer
56 views

How to understand locality and non-locality in Quantum Mechanics?

What actually is the definition of locality and non-locality? Does non-locality in Quantum Mechanics mean however far you separate 2 entangled atoms in space, the 2 atoms can still influence each ...
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0answers
30 views

Quantum perturbation theory recommendations

What are some concise resources, in particular, online resources, for perturbation theory in quantum mechanics? I want something like a crash course to perturbation theory in quantum mechanics that is ...
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1answer
34 views

How to construct the operator and the physical experiment needed to perform an arbitrary 'measurement in a basis'?

I have taken an introductory level course in QM and have covered some advanced topics by myself and don't really understand what it means to 'measure in a particular basis'. A projective measurement ...
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1answer
55 views

Derivation of the low-energy effective Hamiltonian

In the quantum mechanics, the Hamiltonian $H$ satisfies the Schroedinger equation $$ H\psi = E\psi. $$ Suppose that $P$ is a projection operator, and $Q=1-P$. The low-energy effective Hamiltonian is ...
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23 views

Is it possible to change the direction or bend magnetic flux? [closed]

Is it possible to change the direction or bend the magnetic flux according to our wish? What i actually want to do is that if i have a horse-shoe magnet can i bend the magnetic flux which is running ...
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2answers
80 views

Electromagnetic wave and quantum mechanics [duplicate]

I'm very new to physics. I studied and read about quantum mechanics and what the assumptions are (wave particle duality, uncertainty principle, observation, wave function collapse, etc.), but I also ...
3
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1answer
73 views

Permutation symmetry - a continuous symmetry?

From quantum mechanics it is known that permutation between identical particles does not change the Hamiltonian. Assuming that the quantum system consists of a very high number of particles such that ...
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1answer
36 views

two qubits measurment [closed]

Let $$\text{qubit} = \sqrt{\frac{1}{6}} (i∣00\rangle + ∣10\rangle − 2 ∣11\rangle) \, .$$ I need to calculate the probability for each state while measuring both qubits in the standard basis. I did : ...
2
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1answer
37 views

Difference between scattering amplitude and scattering lenght

I'm studying neutron scattering theory and I noticed that one usually writes the scattered wave as a spherical wave: $$\psi \sim \frac{-b} {r}e^{ikr}$$ where $b$ is known as scattering lenght. From ...
5
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3answers
221 views

Reason for Uncertainty principle

$$\Delta x \Delta p_x \geq \frac{\hbar}{2} $$ I understand what does Heisenberg's uncertainty principle states i.e. it's definition and it has been proven experimentally. But, can anyone please ...
1
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1answer
54 views

Time is what keeps everything from appearing at once [closed]

This is a question about time. In this talk http://ed.ted.com/lessons/einstein-s-brilliant-mistake-entangled-states-chad-orzel Chad Orzel makes the point that if the same quantum experiment is ...
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0answers
58 views

Using the double slit experiment to prove or disprove the de Broglie-Bohm pilot wave theory

Probably a dumb question... If you have a double slit experiment with a second experiment (single or double slit) at 90 degrees intersecting the path of the first experiment, would the interference ...
2
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1answer
65 views

Why does circularly polarized light break time-reversal symmetry?

I've encountered some interesting paper on 2D materials where authors use circularly polarized light to break time-reversal symmetry to split energy levels. Here you can find the paper: ...
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1answer
35 views

Probability and double slit

if a beam of identical particles at random distances from each other (or exactly 1/2 lambda between each other) travelling with the same v towards a double sllit do not interfere with each others wave ...
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0answers
29 views

How should we deal with diagrams which do not conserve particle number in a non-relativistic field theory?

In the last 10 years there has been more and more crossover of techniques from high energy physics being used in AMO and condensed matter scenarios, in particular diagrammatic techniques and related ...
2
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1answer
55 views

Is there a mathematical relationship between Legendre conjugates and Fourier conjugates?

In quantum mechanics, there is an uncertainty principle between conjugate variables, giving rise to complementary descriptions of a quantum system. But the variables are conjugates in two different ...
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1answer
107 views

Why does temperature have no uncertainity?

Lets say I have an object A, with temperature $T$ and Hamiltonian $H_{A}$. Now take a thermometer B, with Hamiltonian $H_{B}$. Now when I put the thermometer in contact with A and do a measurement ...
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2answers
64 views

Does calculus work on the quantum scale [duplicate]

I have read somewhere that Leibniz championed the idea that the world is continuous as this was needed for his (or maybe Newtons) new invention (or discovery?) of calculus. But if I am not mistaken a ...
11
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2answers
846 views

Is there experimental verification of the s, p, d, f orbital shapes?

Have there been any experiments performed (or proposed) to prove that the shapes of the s,p,d,f orbitals correspond to our spatial reality as opposed to just being a figment of the mathematics that ...
2
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2answers
66 views

Can I apply $E=hf$ to a particle having mass?

I am reading concepts of modern physics (by Arthur Beiser) where he calculates the de Broglie wave velocity. For that he uses the relation $v = fλ$ where $v$, $f$, and $λ$ are velocity (de Broglie ...
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1answer
77 views

Does the randomness of QM do much in everyday life? How much? [closed]

My apologies if in its current state this question isn't squarely suited here; I've worked it until it seemed reasonably articulate. Feel free to move it if it'd be better received elsewhere. ...
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0answers
48 views

Are photons just electric waves in an electron's frame of reference?

They say that electrons emit photons when they jump to a lower orbit. But the way electrons should see it, there's no any emission, really. There's just rapid change in electric field due to a rapid ...
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3answers
94 views

Both Eigenvalues and Operators are “Observables”? [duplicate]

I am having a bit of difficulty wading through the what seems to be multiple usages for Observables in Quantum Mechanics. " Mathematically observables are postulated to be Hermitian operators.. " ...
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2answers
118 views

Faster-Than-Light Communication using Entangled Photons

Based on my understanding of the “Double-Slit Quantum Eraser Experiment”, documented here: http://grad.physics.sunysb.edu/~amarch/, it seems that Faster-Than-Light communication is possible. Of ...
2
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3answers
114 views

Why photons reflect off glass?

Why photon reflects and refracts through glass? Some photons pass through glass and some reflects.I know this is due to energy levels of electrons of glass, an incoming photon is unable to excite the ...
2
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1answer
80 views

Why isn't the time-derivative considered an operator in quantum mechanics? [duplicate]

Based on my understanding when doing quantum mechanics we deal with a small set of mathematical objects: namely scalars, kets, bras, and operators. But then in the Schrodinger equation we have this ...
2
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1answer
86 views

Is there a reason why a relativistic quantum theory of a single fermion exists, but of a single scalar not?

When we try to construct the relativistic generalization of non-relativistic time dependent Schroedinger equation, there are at least two possible completions - Klein-Gordon equation and Dirac ...
5
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2answers
71 views

What does it mean to observe? [duplicate]

This is a layman's question. The only thing I know about quantum physics is from casual reading and documentaries. I can imagine electrons being probabilistic waves. Their position is an infinite ...
3
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1answer
120 views

Can operators be argument of Dirac Delta function

In one part of Marc Bee's book on Quasielastic Neutron Scattering, he defines the pair correlation function $$ G(\textbf r,t) = \frac{1}{(2\pi)^3}\int I(\textbf Q,t)\text e^{-i\textbf Q.\textbf r}\ ...
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3answers
83 views

Does Bell's theorem exclude local hidden variables as explanation for radioactive decay?

Often it is said that Bell's theorem (and the observed violations thereof) rules out local hidden variable theories as the explanation for the seeming non-determinism found in quantum mechanics. I'm ...