# Tagged Questions

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 quantum-field-...

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### Bosonic Schrödinger field [closed]

When second quantizating the Schrödinger field $$\psi(r,t) = \sum_i \phi_i(r)b_i(t),\quad\mbox{and}\quad \psi^{\dagger}(r,t) = \sum_i \phi_{i}(r)^* b_i^{\dagger}(t),$$ we have the commutation ...
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### Influence of applied voltage to an electron of a metal

I would like to ask what would happen to the potential well of an electron being trapped in a metal? If I apply a voltage trying to accelerate the electron out of the potential well. Would It make the ...
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### Time derivative of $\hat p$ under time varying Hamiltonian

How does one show that $$\frac {d\hat p}{dt} = \frac 1{i\hbar}[\hat p, \hat H]$$ is valid even when Hamiltonian is time dependent explicitly? I can see that this is true when $\hat H$ is time ...
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### How does path integral formulation explain bound states?

It seems to me that the intuitive explanation of path integrals in quantum mechanics describes scattering processes only. You have a particle going from A to B and you compute the probability ...
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### Change in Shannon entropy of a quantum circuit of Hadamard gate and a loop

The following Q&A about reversible computing is available here. It has listed a number of practical scenarios where a reversible circuit can still be dissipating heat. Let's assume that none of ...
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### To what extent can the superconducting order parameter be thought of as a macroscopic wavefunction?

I know that the order parameter does not obey the Schrodinger equation; it instead obeys the Ginzburg-Landau equation. However, I am unclear as to the situations under which the view of the ...
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### Is a wave packet physically realizable as a Fourier series?

In QM a wave packet is modeled as an infinite, or almost infinite, Fourier series, and the Fourier transform provides a transformation between momentum space and position space. To what extent is ...
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### Can Half Lives (hypothetically) be Measured by Wave-functions?

I understand that half-lives are measured over several days/months/years of observing a certain amount of an element and seeing how long it takes to decay a certain amount, but I'm curious as to ...
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### Is the scattering length definitely positive if the potential is everywhere nonnegative?

Is the scattering length definitely positive if the potential is everywhere nonnegative? Intuitively, it seems reasonable. Any rigorous proof?
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### Entangled vectors in hilbert space

We consider a system of two particles of spin $\frac{1}{2}$, each described by the two-dimensional one-particle Hilbert space $\mathcal{H}$. Let $|\pm\rangle\in\mathcal{H}$ denote the eigenvectors of ...
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### Many Worlds or Infinite Worlds?

Looking at the latest paper to deal with the topic: where it purports to show that QM can be recovered from the interactions of a multitude of Newtonian worlds, we have the following statements: ...
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### Proof of inability to obtain global phase

I'm curious if there's a quick proof of the inability to obtain global phase from a quantum state, since they're supposedly indistinguisable. I suppose to measure this, you would need a Hermitian ...
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### What is discrete phase space?

I've been reading a little about the usual, continuous Wigner functions and phase space quasi-distributions in general, and I believe I understand the idea behind them. The Wigner function arises when ...
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### Charge Conjugation Operator in Supermultiplet

Consider an $\mathcal{N}=1$ left-handed chiral supermultiplet. The particle content is $$L = (\phi\quad e_L)$$ where $\phi$ is a complex scalar and $e_L$ a left handed Weyl fermion. People usually ...
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