States Definition and 1000 Threads

Hi folks, I just have a question concerning whether it is possible to produce an ensemble of individual electrons in pure single-particle spin states. I'm assuming it is possible, but sometimes one hears that strictly speaking all electrons are entangled with one another, which would mean...

If problem states "acceleration is constant" what is the acceleration? While gliding down a steep hill, a bike rider experiences constant acceleration. After 4.50 seconds, he reaches a final velocity of 7.50 m/sec. The bike's displacement was 19.0 meters. I know that I'm supposed to be using...

Hi folks, I was just reading about symmetries, and why we say that the two spin states of the electron are states of the same particle, while we are free to say that the two strong isospin states define tow different types of particle. According to the book I'm reading, we must attribute two...

Homework Statement An electron in an infinitely deep potential well of thickness 4 angstroms is placed in a linear superposition of the first and third states. What is the frequency of oscillation of the electron probability density?Homework Equations E=hωThe Attempt at a Solution My main...

Hi, If you have a even-even nuclei which is deformed, you get a rotational spectrum of 0+,2+,4+,... I don't understand why the parities are positive for even I and why all members of a rotational band must have the same parity. I read about this in Krane's book: an introduction to nuclear...

Hi I read this information about the Qubit: "N Qubits are equivalent 2^N classical bits (2^N states)" But I couldn't understand that, because I know that each single Qubit could be one and zero at the same time, so each single Qubit is equivalent two classical bits (two states) That...

Hey guys, I was reading about thermal states and now I have a doubt: is a thermal state always a mixed state with density matrix ρ=exp(-βH)/Tr(exp(-βH)), or is there also a pure thermal state? Thank you

I'm having trouble finding comprehensible explanations of how experimenters can ever know that two particles are entangled. I understand that the first experimental confirmation of entanglement used Calcium or Mercury vapor which when excited gave off pairs of entangled photons. But how did...

Homework Statement I need some help with the following problem: Homework Equations ##\rho(k) dk = \frac{L}{\pi} dk## ##L=Na## ##\omega^2= \omega_m^2 \ sin^2 (qa/2)## The Attempt at a Solution The density of states is given by: ##g(\omega)= \rho (k) / \frac{dw}{dk}## Where...

For an electron gas generated in the inversion layer of a semiconductor interface, my book gives the conduction band density of states for the two dimensional electron gas as: ##g(E)=\frac{L^2m^*}{\hbar^2 \pi}## Where m* is the effective mass of the electron. I can't follow how this was...

According to Griffiths QM book, after he derived the stationary state solutions to the Schrodinger equation for a particle in an infinite potential well, which are just functions of sine, he claims that these stationary solutions are orthogonal and complete. I agree that they are orthogonal...

hi i know what is coherent state, but i read this text in an article and i don't understand this " if we wish to describe long range macroscopic forces, only bosonic fields will do, since fermionic fields cannot build up classical coherent states. " can you explain it for me, how...

Ok, so for some reason this section of the GRE book makes 0 sense to me ... maybe because i haven't taken the class yet, maybe I'm missing something ... It says "If you have a spin-1 particle with m = +1 and a spin-1/2 particle with m = +1/2, then m_tot = +3/2 (this part makes sense, you just...

Hi folks --- I was just reading that entangled states are very much the norm in the universe. Can anybody tell me why entanglement is taken to be such a pervasive feature of the world, so that product states are the exception? Has it got something to do with the fact that strictly speaking all...

I look at wikipedia.org/wiki/Bell_state and use the same notations. The article says that there are just 4 Bell states. Is not |\xi^+\rangle = \frac{1}{\sqrt{2}} (|0\rangle_A \otimes |+\rangle_B + |1\rangle_A \otimes |-\rangle_B) another maximally entangled state? The Schmidt decomposition...

It just occurred to me that I don't know why composites of interacting particles are always in entangled -- as opposed to mere product -- states. Obviously if they are not interacting we will just represent them as being in a product state; but why is it that being in a product state entails...

In the use of the word "causation" can one say that one quantum state "causes" another if the two states are not measured? Or does the concept of causation only refer to a relationship between measurements?

I know how to calculate transition rates between nl resolved states in a hydrogen-like atom, but I don't know how to calculate transition rates between nljm states. I know that dipole transition rate is \frac{32}{3}\frac{\pi^3 \alpha c}{\lambda^3}\left<\psi_1|\mathbf{d}|\psi_2\right> The...

The result of the Kallen-Lehmann spectral representation is that the two point correlation (and thus also the full propagator) has a pole in the physical mass of the particle. In Peskin and Schroeder it is also argued that multiparticle states show up as a cut, but bound states can also show up...

Homework Statement Hi guys, I've recently taken up quantum, so it's all very new to me, it would be greatly appreciated if someone could check my working!Let ψ1(x) and ψ2(x) be two orthonormal solutions of the TISE with corresponding energy eigenvalues E1 and E2. At time t = 0, the particle is...

How is see by our senses a superposition of sensorially distinghible states in superposition, for example, superpositions of states with the same object with a separation of ≈1 cm??

I'm studying the hydrogen atom and have this question. Apparently it can be solved without perturbation theory, however I'm having trouble justifying it. Homework Statement 2. The attempt at a solution Avoiding perturbation theory I simply get: E = E(n) - constant*(mh) where m...

Two questions: If you have two states which have at least one common eigenvalue, then are the two states distinguishable? If you have one state but measure it with two different bases, can one conclude anything if the two measurements have a common eigenvalue? Thanks

The J/Psi is a state of charmonium with J=1, S=1, L=0. So J^{PC} = 1^{--}. It can be excited to states J^\prime \textrm{ and } J^{\prime\prime}, but these don't change any of these numbers. So what is changing?

Hello! I'm having my materialphysics exam in a few days, and looking some of the older exams I saw that there are many times questions about band structure and density of states. More specifically there might be a picture of some band structure plus the density of states, like this. Then...

Are systems ever in a pure quantum mechanical state? If they are, is it possible to know the precise pure QM state? The example I am thinking of is the spin of an electron. If we measure the spin about the "z-axis" and find the result to be "up" then we say the electron is in the pure state...

Hi All! I am doing my Masters project on III-V Nitrides, my question is really a basic one. What are the localized states and what is meant by localization energy and degree of localization, also that excitons are localized to the tail state? Could you please give me an answer and guide...

The following was written down as a solution to a problem, \begin{eqnarray} P(\alpha_n) & = & \frac{1}{25} \left[ 9| \langle \phi_n \mid \psi_1 \rangle |^2 + 16 | \langle \phi_n \mid \psi_2 \rangle |^2 + 12 i \langle \phi_n \mid \psi_1 \rangle \langle \phi_n \mid \psi_2 \rangle^* - 12 i...

Given two spin-1/2 particles, the overall spin of the pair decomposes into a spin singlet and a spin triplet. Using the Clebsch-Gordon series and referring to the z-axis, we find the spin singlet is: ##|\Psi^- \rangle = \frac{1}{\sqrt{2}}(|\uparrow_z \downarrow_z \rangle - |\downarrow_z...

Homework Statement Prove the following theorum: If V(x) is an even function (that is, ##V(-x) = V(x)##) then ## \psi (x) ## can always be taken to be either even or odd. Hint: If ## \psi ## satisfies equation [1.0] for a given E, so too does ## \psi (-x) ## and hence also the odd and...

Feynman diagrams is the standard for calculate the probability of nuclear reactions fo particles, but, when we want calculate the probability of evolution of an arbitratry field to another field a fixed time after, what is the mechanism??

Any two dimensional state can be written as: |\phi\rangle=\cos\frac{\theta}{2}|0\rangle+e^{i\phi}\sin\frac{\theta}{2}|1\rangle where 0\leq\theta\leq\pi and 0\leq\phi\leq 2\pi, and 0\leq\theta\leq\pi. To pick one such state uniformly at random it suffices to draw \phi at random from its...

Good morning everyone ! I've been reading discussions on PF for a long time, but here I'm stuck on a little problem that really annoys me and I couldn't find answer anywhere, so I guess it was time to register. :> I've been focusing on quantum electrodynamics for a couple of weeks now as part...

Homework Statement Hey all, I am having trouble following some of the notes that my professor posted with regards to waves inside a blackbody; here is what he posted: (the part in bold is what I am just not understanding) "Inside the blackbody box, we need for the position of the walls...

Hello! I am having trouble using the SimPowerSystems library from simulink to simulate circuits (with the powergui solver). On all the circuits I have simulated so far either of the following happens: - Adding the initial current/voltage directly at the RLC branch block culminates into...

In my text: The number of states per unit volume of the real space & the reciprocal space is given by 1 / (4∏³) No further explanation is given. How do you get to this 4∏³ And how come the density of states is the same in real space & reciprocal space? I think this is...

The Wigner function, W(x,p)\equiv\frac{1}{\pi\hbar}\int_{-\infty}^{\infty} \psi^*(x+y)\psi(x-y)e^{2ipy/\hbar}\, dy\; , of the quantum harmonic oscillator eigenstates is given by, W(x,p) = \frac{1}{\pi\hbar}\exp(-2\epsilon)(-1)^nL_n(4\epsilon)\; , where \epsilon =...

Hello I understand how to approach finite potential well. However i am disturbed by equation which describes number of states ##N## for a finite potential well (##d## is a width of a well and ##W_p## is potential): $$ N \approx \dfrac{\sqrt{2m W_p}d}{\hbar \pi} $$ I am sure it has something to...

I heard that light in a medium can have longitudinal polarization i.e the e field in the direction of propagation, but i saw in a qed course that light can have temporal or scalar polarization (the E0 component). What is that one and how can one obtain this kind of polarization experimentally ...

Homework Statement Wow, the site looks way different from when I was last here. Nice job to whoever did this! Now, to business... My question pertains to part 2a of the HW. I've gotten the wavefunction in terms of the spherical harmonics, but I need help bringing it on home, so to...

0.05KG of steam at 15bar is contained in a rigid vessel of volume 0.0076 m3. What is the temperature of the steam? If the vessel is cooled, at what temperature will the steam be just dry saturated? Coolingis continued until the pressure in the vessel is 11 bar; calculate the final dryness...

Homework Statement A particle of mass m in the infinite square well of width a at time t = 0 is in a linear superposition of the ground- and the first excited- eigenstates, specifically it has the wave function $$| \Psi(x,t) > = A[ | \psi_1 > + e^{i \phi} | \psi_2 >$$ Find the...

Homework Statement Use the relationship kinetic energy E = p^2/2m to show that the energy E_{0} of an electron of mass m in its lowest energy state is given by E_{0} = h^2/8mL^2 Homework Equations E = p^2/2m E_{0} = h^2/8mL^2 The Attempt at a Solution I've stared at this...

Homework Statement Hello, I am required to determine the total number of micro states of a system in equilibrium within a certain value, 1/σ. The number of micro states for this system is given by, \Omega...

The formula for density of states in a free electron gas is g(E) = (3/2) (n/E_{F})\sqrt{E/E_F}. However, this looks like it has no direct dependence on temperature. It seems that only the probability of electron occupation of a state changes with temperature, not the number of states itself...

So munkres states that equicontinuity depends on the metric and not only on the topology. I'm a little confused by this. Is he saying that if we take C(X,Y) where the topology on Y can be generated by metrics d and p, then a set of functions F might be equicontinuous in one and not the other...

Polarization states "directly measured": What did this experiment do? I ran across, on phys.org, this fairly pop-sciencey RIT press release: http://www.rochester.edu/news/show.php?id=5692 It describes an experiment which sounds very interesting, but the way the experiment is described is...

The density of states at the fermi energy is given by D(E_F)=(3/2)n/E_F I understand the density of states is the number of states per energy per unity volume, accounting for n/E_F. I don't understand how the 3/2 multiplying factor accounts for the volume?

The state of stress at ##\mathbf{P}##, when referred to axes ##P_{x_1x_2x_3}## is given in ksi unites by the matrix $$ [t_{ij}] = \begin{bmatrix} 9 & 3 & 0\\ 3 & 9 & 0\\ 0 & 0 & 18 \end{bmatrix}. $$ Determine (1)the principal stress values at ##\mathbf{P}## and The trace of...

Hi I have three states (I believe bell states) and want to find the density matrix, am I right in thinking: 1) \frac{|00> + |11>}{\sqrt{2}} \rightarrow \rho = \left( \begin{array}{cc} \frac{1}{\sqrt{2}} & 0 \\ 0 & \frac{1}{\sqrt{2}} \\ \end{array} \right) (because it is pure) 2)...