States Definition and 1000 Threads

Look at the following attached picture, where they prove the coherent states are eigenfunctions of the annihiliation operators by simply proving aexp(φa†)l0> = φexp(φa†)l0>. I understand the proof but does that also prove that: aiexp(Σφiai†)l0> = φiexp(Σφiai†)l0> ? I can see that it would if you...

Homework Statement A particle is in the state |\psi \rangle = \frac{1}{{\sqrt 3 }}|U\rangle + \frac{{a\sqrt {(2)} }}{{\sqrt {(3)} }}i|D\rangle . The up state |U\rangle = \left( {\begin{array}{*{20}{c}} 1\\ 0 \end{array}} \right) and the down state |D\rangle = \left(...

Hi, For the past couple of days I've been attempting to derive the equality (for any normalised ##\varphi##) ||(a+za^\dagger+ \lambda)\varphi ||^2 = ||(a^\dagger+\bar{z}a+ \bar{\lambda} )\varphi ||^2 + (|z|^2-1)||\varphi ||^2 First of the summation seemed like a typo. So I first tried to prove...

What is the value of ##\left\langle {{\bf{p}}|{\bf{p}}} \right\rangle ## when ##a_{\bf{k}}^ + k\left| 0 \right\rangle = \sqrt {2{E_{\bf{p}}}} \left| 0 \right\rangle ##? (like in Peskin) I suppose that ##\left\langle {\bf{k}} \right|{a_{\bf{k}}}{\bf{P}}a_{\bf{k}}^ + \left| {\bf{k}}...

Homework Statement "Show that the Slater Determinant states are a complete basis" is the entire statement. Homework EquationsThe Attempt at a Solution I guess I'm trying to prove that the rank of the states is equal to the basis? I'm not sure where to start on this one.

In case you haven't come across it yet, there is a very informative overview of the history of physics education in the US, starting all the way from the 1860s. D.E. Meltzer and V.K. Otero, Am. J. Phys. v.83, p.447 (2015). It is 12 pages long, and covers some of the most significant movement...

if in a hydrogen atom the electron is in a excited state, is the net charge the same vs ground state? what is the difference between charge and energy here? thx

Homework Statement Recall the definition of the overlap of wave functions Φ and Ψ: [; (\Psi , \Phi ) = \int\limits_{-\infty}^\infty dx\: \Psi ^{*} (x)\Phi(x);] Let ψ1(x) and ψ2(x) be unit-normalised wavefunctions representing sharp-energy states with different energies (and hence zero...

Here is a thought experiment. Imagine Schrodinger's cat... in the traditional model, there is a single observer outside the box, and the observer creates an entanglement with the catbox device which reveals the quantum superposition of the enclosed cat. The cat is said to be in a superposition...

Hi there! As you might have already guessed, I'm referring primarily to the 'geometrical' difference (is there such geometry in Hilbert space?) between ##n##-dimensional state vectors | \psi \rangle = \left( \begin{matrix} \psi_1 \\ \psi_2 \\ \vdots \\ \psi_n \end{matrix} \right) and their...

Hello! Does anybody know how to calculate the DOS as a function of Neff and λ/Λ? Thanks.

Are all quantum states represented by normal vectors?

Hello! I know how to calculate band structure and density of states of photonic crystal (example is pic.1) Does anybody know how to plot such DOS maps? The second picture is from the article about photonic crystal fibers by Rodrigo Amezcua.

According to my thermo textbook the density of states should really be called the density of orbitals because "it refers to the solutions of a one particle problem and not to the states of the N particle system". This makes perfect sense to me but now I'm confused about references to the density...

Hello there, I am just starting quantum physics with the textbook by griffiths. My lecturer has told me that the set of functions representing stationary states in Hilbert space forms an orthogonal set. He was however unable to prove it. Furthermore he said that it is not always the case, but...

Hi. Look at the picture on 1:28 and 1:37 in this video: How is it possible that the fermi-level is between two energy bands? The fermi level is defined as the highest energy level that contains an electron 50% of the time, so how is it possible for the fermi level being in an area that is...

Homework Statement A system has two independent states ##|1\rangle## and ##|2\rangle## represented by column matrices ##|1\rangle \rightarrow (1,0)## and ##|2\rangle \rightarrow (0.1)##. With respect to these two states, the Hamiltonian has a time independent matrix representation...

Hello everyone. Can someone explains me the meaning of quantum state transition? For example consider an electron which is in the superposition of two energy eigenstates of a given hamiltonian, now, if no one perturbs the state with a measure, nothing happens and the superposition remains the...

Homework Statement Show that it is always possible to adjust measurement units such that a; b can be assigned any values you want. This means that e.g. all van der Waals gases look exactly the same if the units are accordingly adjusted. (This is what is called principle of corresponding...

It's known that the number of states in a band is equal to the number of unit cells in crystal. Here is my problem (confusion with trivial concepts) Bloch function is a electronic state, or orbital. The number of orbitals in a band inside the first zone is equal to the number os units cells...

Dear All: I'm very confusing with the relationship between photonic local density of states and the field intensity. In thermal equilibrium, the field intensity should be proportional to the photon's number (or squared) and also be proportional to the local density of states. We know that this...

Okay, here goes... Our teacher set a question in the last test which asked us to show that if a system initially be in a stationary state, it will remain in a stationary state even if the system evolves according to the time dependent Schrodinger equation. What I did was show that the...

The question is for which of the ##1P## meson states - ##1^{1}P_{1}, 1^{3}P_{0},1^{3}P_{1}, 1^{3}P_{2} ## ##D_{s}## states decaying to a ##1S## state is the decay: ##D_{s}**^{+} -> D_{s}^{+}\pi^{0} ## possible? Solution So the strong interaction conserves parity. Parity of meson is given by...

Hi all, In Charles Kittel (Introduction to Solid State Physics) He writes : U (Total Phonon Energy ) = Σk∑p((ħ*ωk,p)/((exp(ħ*ωk,p/τ))-1)) I understand this, but then he integrate over k and multiply by density of states : U (Total Phonon Energy ) = ∑p∫dω*Dp(ω)*((ħ*ωk,p)/((exp(ħ*ωk,p/τ))-1))...

Hey! :o Prove that for each $n>0$, a language $B_n$ exists where $B_n$ is recognizable by an NFA that has $n$ states, and If $B_n=A_1 \cup \dots \cup A_k$, for regular languages $A_i$, then at least one of the $A_i$ requires a DFA with exponentially many states. Could you give me some...

I have looked around for help with this, including on existing threads, but I can't quite find what I'm looking for. I know that in the nuclear shell model we fill the shells in the same way as with electrons, so 2 protons in the first and 6 in the second etc, with the same being true for...

Homework Statement When calculating expectation values for spin states I encountered ##\langle \hat{\mathbb{S}}_+\rangle = \langle+z|\hat{\mathbb{S}}_+|+z\rangle = \frac12\langle+z|\hat{\mathbb{S}}_++\hat{\mathbb{S}}_-|+z\rangle.## How do we compute...

Folks were celebrating when these states joined the EU. http://www.dw.de/the-baltic-states-from-soviet-to-european/a-17872310 But now, folks are wearily eyeing a more aggressive Russia next door, especially after the Russian annexation of Crimea and invasion of Ukraine's territory. Meanwhile...

It is stated that classical states are robust against decoherence.. what would happen if classical states can decohere too? Or how do you imagine it for example occurring to a table.. How would the table look like if it suffers decoherence too? Would you fall down if you sit on one?

I've been following the EdX course on Quantum Computing by Prof. Vazirani and I don't understand how one physically can create a superimposed state of the ground and 1st excited state of an hydrogen atom. He mentions "the use of light," but doesn't explain the frequency of the light, nor the...

I think I have read that massless fermionic states can be used (as a basis?) to build up massive fermionic states. Is that true? If so, could you please give me a very short outline of how this is done, or maybe better, a mathematical statement that "says" the same thing? Thanks for any help!

Homework Statement Consider three electrons in three different orbital levels n, m and p. We assume that there is one electron in each orbital level. How many states are then possible? Homework Equations Equations for constructing symmetric and asymmetric wavefunctions: Symmetric under pair...

Are there any known (collective spin) operators to raise or lower the quantum number s in \left|{s,m}\right> spin states? I'm trying to construct coherent states varying the quantum number s instead of the well known spin coherent states varying m. I found a coherent-like state similar to the...

How do I write the general form of a 3 qubit mixed state ? It has 63 variables. Well one way is to use bloch vectors. So basically we take 3 single qubit mixed states (3 variables each) and tensor product them. Then we add the 2 qubit correlators and 3 qubit correlator terms. Finally we can...

Things I don't understand: What do they mean by "two spin-1/2 doublets and a spin-3/2 quadruplet"? Why do they use the two flavours "+2/3e and -1/3e" ?

In wien2k software of Dft how we came to know specific states like 3p 2s 4d etc peaks in total density of state of a compound.how we can relate TDOS with bandstructure.

While browsing Wikipedia I bumped into this sentence that seemed partially wrong to me but maybe I didn't understand what it is referring to so would like for some expert to help me elucidate it: "Even if an elementary particle has a delocalized wavepacket, the wavepacket is in fact a quantum...

Homework Statement Evaluate the matrix elements ## {\mathbb S}=\left( \begin{array}{cc} \langle x|\mathbb{\hat J}_z|x\rangle& \langle x|\mathbb{\hat J}_z|y\rangle\\ \langle y|\mathbb{\hat J}_z|x\rangle &\langle y|\mathbb{\hat J}_z|y\rangle\end{array}\right)## by expressing the linear...

Homework Statement I'm curious in proving that expectation value of momentum for any bound state is zero. So the problem is how to prove this.Homework Equations $$ \langle \mathbf{p_n} \rangle \propto \int \psi^*(\mathbf{r_1}, \dots ,\mathbf{r_N}) \nabla_n \psi(\mathbf{r_1}, \dots...

I know that matter can only exist in one state at a time; however at the quantum level knowing what state it is in at a set time is impossible to know for sure until you look at the system. Like with how Schrodinger cat is in a state of randomness between the two states of dead and alive until...

Is it possible, in principle, for an experiment to distinguish between an ensemble of pure states and an ensemble of mixed states? If so, how? In particular, I am thinking of an ensemble of particles whose spin has been measured, one at a time, on the "Vertical" axis. The ensemble consists of...

How do you understand pointer states? I was trying to comprehend Zurek papers that without Einselection, Decoherence can even affect classical states and every tourist who looks at the Statue of Liberty would see different thing because its state was affected by the previous tourist. So he...

I have a theoretical question, I just recently learned that the spin triplet S=1 of helium in the state 1s2s is lower in energy than the 1s2 state due to the exchange interaction. I then learned that this 1s2s state has a shorter lifetime than the 1s2 state, can anyone explain why this occurs...

In The Theoritical Minimum we shown all spins states use just two states up and down. How can we do that.? I am confused about the directions of states and normal coordinate system Can somebody help me ? Thanks

I am reading a book The Theoretical Minimum I didnt understand spin and quantum states "All possible spin states can be represented in a two dimensional vector space." What it means ?

I have a question concerning the paper "Quantum imaging with undetected photons". http://arxiv.org/abs/1401.4318 In the schematic (Fig. 1) a photon (idler) is created at NL1 and passing the object at O to be reflected further to NL2. It is then stated in the paper "By reflection at dichroic...

Hello, I am calculating the potential energy surface of an iron slab, once with a ferro magnetic behavior and later anti ferromagnetic behavior, I know for ferromagnetic I multiply the number of atoms by its magnetic moment (I use 3 that must be a little higher than its real value), my...

Homework Statement http://web.phys.ntnu.no/~kolausen/TFY4230/.oldExams/17_eksdes12.en.pdf solution: http://web.phys.ntnu.no/~kolausen/TFY4230/.oldExams/18_losdes12.en.pdf Look at problem 4a, formula (27) or the expression between (29) and (30). My professor keeps converting sums into...

(This though came up while learning about band structure, so that is how I am going to explain it, but I think it applies equally well to a square well, for example). Say you have an electron at the Fermi level of an insulator. Then, you apply an electric field. No current flows, because all...

Ok, so what I considered to be true for quite some time now has been somewhat tarnished after something that was said recently in a lecture, so I am looking for some insight. Basically, I was told several times by several teachers/professors over the years that when an electron absorbs a...