I'll use a hydrogen atom as an example. A hydrogen atom has multiple energy eigenstates for all but one of its energy levels. Suppose I measure a hydrogen atom to have an energy $E_n$ where $n > 1$. What's the state of the hydrogen atom right after my measurement?

i would like to know if it is possible to create constant energy,using a special compartment that funnels the vacuum of space to spin a turbine and also utilising the friction created to provide further energy that wont run out.the funnel itself will create extra suction that circulates around va...

In Section 21 of "Quantum Field theory" by Mark Srednicki, it is shown that there are two equivalent ways to get the quantum action of the shifted field $\phi'= \phi-\tilde{\phi}$, where $\phi$ is the original field and $\tilde{\phi}$ is the background. (See Eq. (21.27)) One way is to first perf...

I was learning Basic Quantum mechanics. I cam across the fluid equation in QM, which suggest psi(star)*Psi is probability density function. Consider the two statements below 1)Probability will change with time. If probability of finding a particle at one place os increased, then the prob...

Basically, my question is whether there are methods to monitor mass position with an interaction Hamiltonian followed by a measurement of the detector wave function, as in an Arthurs and Kelly scheme. As far as I know, the measurement of the particle (or mirrors in the Gravitational Wave Detector...

Question from lecture notes: What of the following operators does not commute with $\hat x$? A. $ \hat L x $ B.$ \hat Ly $ C. $ \hat Lz $ D. None of the above. The answer is A. But when I compute this myself, the answer is $0$, indicating they do commute, yes? Here is my work: $$[\hat x, ...

I will give a few examples to explain my question 1)Suppose we send a beam of light through a beam splitter which splits the beam into upper and lower branches . Then they interfere constructively and destructively at the two detectors. We know photons cant interfere with each other as it would v...

So I am reading this paper, which states multiple times that: Indeed, global (and thus entangling) unitary operations are capable of extracting more work than local operations from a set of quantum systems. And towards the end the 'conclusion' reads: So the farther $\sigma_{\mathrm{th...

In almost all the books on Quantum Mechanics, it is stated that if $|\alpha \rangle $ is a ket describing the state of a system, then any observable has a set of eigenvectors s.t those eigenvectors form a basis for the Hilbert space of all possible states $|\beta \rangle $ that that sy...

I am now reading my lecture notes on dipole moment and there's a point which confused me. It says that: Let us consider the |1S> and |2P_x> states of a hydrogen atom. The atom has inversion symmetry, so all the eigenstates have either even (such as |1s> ) or odd (such as |2p_x>). Therefore, w...

If you have two fermions (with spin $\pm \frac{1}{2}$) that form a weak-isospin doublet and their respective right-handed fermions which are weak-isospin singlets, what would it imply if the doublet had the weak hyper charge $0$ ? How would the particles couple to the photon and the Z boson? F...

I posted this question in History of Science and Math but did not receive a response. Does anyone know the earliest reference where the atomic orbitals (s,p,d,f) were depicted graphically? Although Schrodinger proposed the wave equation, surprisingly, the famous collected papers of Schrodinger ti...

On page 200 of Auletta, Fortunato and Parisi's textbook on Quantum Mechanics they write: Here $\hat{\mathbf{l}}$ is the operator corresponding to the magnitude of angular momentum and $l$ its maximal eigenvalue of $\hat{l}_z$. I have read through the section carefully and they seem to be confusi...