State Definition and 1000 Threads

Imagine a two-state system, e.g., a single nucleus that can be aligned or anti-aligned with an external magnetic field. If that nucleus is in a "mixed state" at time zero, such that it's wavefunction is 50% up and 50% down at time zero, why can that nucleus absorb a "quanta" of radiofrequency...

Homework Statement (Note: this is the last part of a longer problem, so I hope I won't miss anything important) We have a laser with 2 energy levels, so the emitted photons will have the energy ##\omega##. For this given energy there are ##m## states in which the photon can be, denoted...

Homework Statement Is the following matrix a state operator ? and if it is a state operator is it a pure state ? and if it is so then find the state vectors for the pure state. If you don't see image here is the matrix which is 2X2 in MATLAB code: [9/25 12/25; 12/25 16/25] Homework...

In the four-observation method of Gauss for orbit determination, the right ascension and declination of an asteroid is observed at specified times, and the heliocentric position of Earth is obtained from tables (or JPL Horizons) for those same times. I can follow the procedure to the point...

I start by outlining the little I know about the basics of quantum field theory. The simplest relativistic field theory is described by the Klein-Gordon equation of motion for a scalar field ##\large \phi(\vec{x},t)##: $$\large \frac{\partial^2\phi}{\partial t^2}-\nabla^2\phi+m^2\phi=0.$$ We...

I know that Bragg reflection in solid states at the edge of e.g. the first Brillouin Zone causes standing waves at these edges, which creates a gap between the energy bands. In this picture below you can see the probability density of a symmetric (+) and anti-symmetric (-) standing wave. The...

Hi. Please excuse my ignorance but this entire volume translation formulas for EOS confuses me to no end. Could someone tell me how the volume-translated Peng-Robinson exactly works? How do I calculate the fugacity expression of VTPR? Do I integrate the V + c terms against dV or do i integrate...

In the last paragraph of these notes, https://ocw.mit.edu/courses/physics/8-04-quantum-physics-i-spring-2016/lecture-notes/MIT8_04S16_LecNotes3.pdf, it says how a state with large number of photons is not classical. Why is that? I thought quantum mechanics' laws were most applicable when we...

Homework Statement A certain odd-parity shell-model state can hold up to a maximum of 4 nucleons. What are its values of J and L? What about an odd-parity shell-model state with a maximum of 6 nucleons? Homework Equations Parity = (-1)L J = L+S Total angular momentum, J, is equal to orbital...

I got invited to visit Washington on winter next year. Not knowing the geography of the states, I checked on the map and my immediate reaction to my friend was: "Uff! That's almost in the North Pole!" :DD I'll have to think about it. Cold and me do not mix well. Jokes aside, I realized how...

@mfb From this thread - https://www.physicsforums.com/threads/why-doesnt-the-plate-interact-with-the-particle-in-double-slit.949489/ Post #2 - "It is not feasible to keep such a large and especially a biological object in a state without measurement" How does one keep a multi-particle...

WHERE is the refrigerant stored in the refrigeration system when the system is in OFF and in WHAT state Gas or Liquid ?

Hi. Is it correct to say that an inductor with a state, that is some level of current inside it, and a capacitor with some voltage, are equivalent to a current source (in the case of an inductor) and a voltage source (in the case of a charged capacitor) respectively at that instant of time? Of...

Hi everyone, I am doing a time dependent perturbation theory, in a case when the electron is prepared in a state of the continuous part of the energy spectrum. Existence of the discrete part and the degeneracy of the continuous part is irrelevant at the moment and will not be considered...

I'm watching a lecture and the professor is talking about generic quantum states as |\psi> He's making the point that this state is very generic. It can represent anything. He references some examples like the polarization of a photon and the path of a photon and the spin of an electron...

If we consider a singlet state : $$(|+-\rangle-|-+\rangle)/\sqrt{2}$$. And operators $$A=B=\textrm{diag}(1,-1)$$ I saw in a lecture that we can consider $$A\otimes B$$, it has multiple eigenvalues 1 and -1. It was then said : we can choose orthonormal basis vectors in each eigenspace. Hence...

How do i apply the laws of refraction to plane and curved surfaces. I have absolutely no idea how to even start on this one, its got nothing to do with the course, i am going to study. i need to understand this to move on but i genuinely have absolutely no interest in optics. I really can not...

> Operator $$\hat{A}$$ has two normalized eigenstates $$\psi_1,\psi_2$$ with > eigenvalues $$\alpha_1,\alpha_2$$. Operator $$\hat{B}$$ has also two > normalized eigenstates $$\phi_1,\phi_2$$ with eigenvalues > $$\beta_1,\beta_2$$. Eigenstates satisfy: > $$\psi_1=(\phi_1+2\phi_2)/\sqrt{5}$$ >...

Homework Statement The isobaric expansion coefficient and the isothermal compressibility are given by: $$\alpha_p = (1/V)(\partial V/\partial T)_p \quad \kappa_T = -(1/V)(\partial V / \partial p)_T$$ Suppose they have experimentally been determined to be: $$ \alpha_p = \frac{1}{T} +...

I was wondering how the rules work for observation in a quantum system. Particularly, about what happens if two separate entities try measuring at the same time. And also, what kinds of interactions are happening all the time that are considered measurements, for example in quantum...

Can someone explain the meaning of the k vector and the general meaning of this equation?

Homework Statement [/B] Estimate the lifetime of the excited state of an atom whose natural emission line width is 3.00 × 10−4 eV. Homework Equations $$ \Delta E \Delta t = \frac{1}{2} \times \frac{h}{2\pi} $$ $$ \Delta E \Delta t = \frac{h}{2\pi} $$The Attempt at a Solution I think all I...

Hi there. I am working on some exercises where they ask about the steady state of a pendulum. I have had quantum mechanics, where the steady state meant a time independence. But I don't really see what this means for a pendulum. Is it steady when it's velocity is zero so there is no time...

Biohackers are mostly "amateur" molecular biologists who (often) want to make new things through genetic engineering. They have been developing their methods and on-line communities. Here is a fairly long NY Times article that gives some background and discusses different sides of regulatory...

There are two types of finite state machines (at least that I know about), mealy and Moore. What are the practical differences between them. I understand that mealy machines take the input into account for the output logic, but are the two machines used for different purposes? Or can the same...

Homework Statement One end of a solid cylindrical copper rod 0.200 m long and 0.0250 m in radius is inserted into a large block of solid hydrogen at its melting temperature, 13.84 K. The other end is blackened and exposed to thermal radiation from surrounding walls at 500.0 K. (Some telescopes...

How does one determine the state of a system from observations? Let us look at a simple example: the spin of a fermion. Any state of the system is a superposition of up and down eigenstates. Denote the coefficients in this superposition by a and b. The question here amounts to determining a...

Hello! If the Library of Babel has 10^(2,000,000) books, does anyone think that it is possible to create a quantum state (with a quantum computer) that represents this Library? I think that in a classical way it is impossible, but in a quantum way? I find it quite interesting! What about you? :)

Homework Statement Considering the molecule of ##C_2^+## in an excited state with valence configuration ##2\sigma_g^2## ##2\sigma_u^2## ##1\pi_u^2## ##3\sigma_g^1##. Finding all the possible term symbol. Homework Equations Term symbol ##^{2S+1}\Lambda## ##L=0 \rightarrow \Sigma## ##L=1...

In Zettili's Quantum Mechanics, page 477, he wants to determine the energy and wave function of the ground state of three non-interacting identical spin 1/2 particles confined in a one-dimensional infinite potential well of length a. He states that one possible configuration of the ground state...

Homework Statement I have derived the differential equations of a system. They are like the following: a\ddot{\theta} - b\ddot{x} + c \theta = 0 \\ d\ddot{\theta} + e\ddot{x} = F(t) where a,b,c,d,e are constants. I'm having trouble putting it into state space form, since I have the highest...

Hi. I have read somewhere that cubic equations of state seem to have convergence issues when vapor pressure calculations are done near the critical point. Sadly, I have forgotten where I have have read it :( I would like to ask some knowledgeable people regarding this, or can people point me I...

im curious as this question came up in a chemistry forum and it's more of a physics question I believe . State changes between elements of near similar number , what constitutes the extreme phase changes ? It was answered that there is no real answer for why the phase differences occurs at...

Homework Statement Calculate the output function and draw a graph of output voltage in the function of the input voltage of the following digital circuit: Homework Equations 3. The Attempt at a Solution [/B] By analysis of what happens when inputs A and B are on the logical "1" i have...

Homework Statement If possible could someone have a look at my working for this problem, I am not sure if I have carried out part b) correctly. I have done all three problem and carried through my solution to b) just to see if it did simplify out, which it didn’t which make me think I may have...

Hi physicsforums, I am an undergrad currently taking an upper-division course in Quantum Mechanics and we have begun studying L^2 space, state vectors, bra-ket notation, and operators, etc. I have a few questions about the relationship between L^2, the space of square-integrable complex-valued...

Actually while studying the inflation phenomenon the transition of the slowly rolling scaler field from from the false vacuum to true vacuum state to a more classically stable state I actually didn't understand this transition from false vacuum to true vacuum and what actually they mean? Another...

Okay, so I've been set this homework to find the normalisation constant, N, for the radial wave function in the 2s state for hydrogen (my title was too long to fit that vital information in). thing is; I'm having a bloody hard time and in the process confusing myself with trying to take out all...

What exactly is the so-called "Ground State Lamb Shift". It seems to have been an 'in vogue' quantity up till 1995 or so - then vanished from the literature ?? It's the 'self energy' or something like that of an electron in H 1S orbital. A scientist (at NIST) told me it's a term that has gone...

If the universe was in an energy eigenstate then d<A>/dt = 0 for any dynamic variable A. Stuff moves which implies that the Universe isn't in an eigenstate. What factors drive the energy spread?

So if string theory is to be correct it must be able to come up with the observed value for the energy density of empty space which is pretty close to zero? A naive understanding of the compact spaces of string theory tells me that an "energy audit" of the highly curved compact manifolds of...

I am having a doubt that if Id lho potential is Given of the form λ2px2/2m+.5kx2 then whether the ground state energy of the system is λ2/4ħω+1/4ħω

Homework Statement Show that any plane wave can be written as the sum of a left-circularly polarized wave and a right-circularly polarized wave of suitable amplitudes and phase Homework EquationsThe Attempt at a Solution If I assume the plane wave polarizes in the z direction. It is possible...

Hi all, There is this question; Firstly, I am new to quantum mechanics and there are a lot of terms I am unfamiliar with. So there is this question that asks me to develop a method to reconstruct state and I have no clue how I should start with. Any help or steps to solve this type of...

I've heard that the average homeowner in the state of Massachussetts (MA) pays about $15,000 in state property taxes per year. I believe that the standard deduction on Federal income taxes is $6,400 per year. State property taxes can be itemized on Federal income taxes. It seems to me that...

how to calculate , oxidation state of polyatomic ions like " acetate" C2H3O2 2(4)-3-4= +1 ? how do we know when carbon or hydrogen are sharing x electrons

Homework Statement For the state ##(4|00\rangle+3i|11\rangle)\otimes (|0\rangle+i|1\rangle) + (2|01\rangle -i|10\rangle)\otimes(|0\rangle-|1\rangle)## What's the probability of zero being the outcome of measuring the second bit and what is the state of the other two qubits after measurement...

Definition 1 The von Neumann entropy of a density matrix is given by $$S(\rho) := - Tr[\rho ln \rho] = H[\lambda (\rho)] $$ where ##H[\lambda (\rho)]## is the Shannon entropy of the set of probabilities ##\lambda (\rho)## (which are eigenvalues of the density operator ##\rho##). Definition 2 If...

[Update December 2021: This is an old thread. I updated it to add a factoid (go to the last post).] I’m on the road again, this time to Florida. Meet a couple of friends of mine in Harlem, Georgia...

I've been reading these notes: http://www.vcpc.univie.ac.at/~ian/hotlist/qc/talks/bloch-sphere-rotations.pdf And on slide 11, to check what the rotation operator is doing, the state is pre- and post-multiplied by the operator so that the calculation performed is ##\rho' = R\rho R^{\dagger}## Why...