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 ...

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scattering theory textbooks

I am looking for a possibly extensive list of great textbooks on elastic and inelastic scattering of particles within quantum field theory. So far i am familiar with: -Peskin and Schroeder: An ...
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24 views

Commutativity of Position Operators

Does the position operator $q_{i}$ of one harmonic oscillator commute with the position operator $q_{j}$ of another different harmonic oscillator? In other words, is $q_{i} q_{j} = q_{j} q_{i}$ true? ...
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time evolution of a quantum system

A quantum system has Hamiltonian H with normalised eigenstates $\psi_n$ and corresponding energies $E_n$ ($n = 1,2,3...$). A linear operator $Q$ is defined by its action on these states: $$ Q\psi_1 = ...
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Require Help for Graphene Based experiments

I really need a software that can help me with graphene based experiments. Is there a software which could allow me to run all types of simulations for graphene layers focusing on photovoltaic cells? ...
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25 views

Momentum of electron problem

Recently, my friend bemused me with a question related to the momentum of an electron. The confusing logic is stated below: Since an electron is a particle and according to classical physics, we know ...
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43 views

General wave packet in Schrödinger equation?

Can I state general wave packet in arbitrary potential $V(x)$ in the following form? $$\psi(x,t) = \frac{1}{\sqrt{2\pi \hbar}} \int \hat{\psi}(p,t) e^{ipx/\hbar}dp=\frac{1}{\sqrt{2\pi \hbar}}\int ...
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21 views

How to make scattering matrix? [on hold]

I need to make a scattering matrix. Potential is unknown. I have the list of scattering data: time, mass and coordinate of the particle. How to make scattering matrix by the given data?
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3answers
112 views

Can a bullet really fly through space forever?

Some people says that if it would be possible to shoot a bullet so high that it would get over the Earth gravitational pull, the bullet could fly through space forever, because of no deceleration of ...
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16 views

How is it shown that the composition of two real operators is generally not real? [duplicate]

Dirac on page 28 of his QM book writes: Thus the conjugate complex of the product of two linear operators equals the product of the conjugate complexes of the factors in the reverse order. As ...
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21 views

Entanglement g-2-experiment - Which components do I need?

I would like to measure whether my source emits entangled photon pairs. To that order I want to build a g-2-experiment, which measures photon coincidence counts as a function of time delay between ...
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26 views

How to construct this oracle quantum gate?

I was reading the paper Quantum Computational Complexity in the Presence of Closed Timelike Curves. In this the author mentions that following quantum oracle gate which operates on $n+1$ qubits, can ...
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48 views

Does a normal torch emit entangled photons?

I was reading a sciencenews.org post about three photons being entangled. My question here is, why is the chance of producing an entangled pair once in a billion times? Isn't every particle produced ...
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32 views

Why a hole in the Dirac sea can be seen as having opposite energy?

In the Dirac's old attempt of relativistic quantum mechanics, a hole in the $E'$ level of the Dirac sea was interpreted as a particle of opposite charge and positive energy. I do get why it can be ...
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18 views

What methods exist to calculate the density of states in the continuum of a molecule?

Say I have an arbitrary molecule in the Born-Oppenheimer approximation, and furthermore say that I can approximate the molecule as having only one active electron. What methods exist to calculate the ...
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43 views

How many wavefunctions are in a minimal basis set for benzene?

I am reading Modern Quantum Chemistry by Szabo and Ostlund and on page 62 he says "A minimal basis set for benzene consists of 72 spin orbitals." I tried to understand this number but failed. ...
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35 views

Quantum physics presentation topic [on hold]

i am doing my advanced quantum mechanics course and the instructor want me to deliver a presentation end of the course.. The topics are: Born-Oppenheimer Approximation → Berry Phase Non-Hermitian ...
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236 views

Tensor product notation convention?

For two particle state, the Dirac ket is writren as $$\lvert\textbf{r}_1\rangle \otimes \lvert\textbf{r}_2 \rangle. $$ Then how do we write its bra vector, $$\langle\textbf{r}_1\rvert \otimes ...
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20 views

Does it matter in which order settings will be changed during CHSH-inequality check experiment?

Does it matter in which order detector settings will be changed when checking CHSH inequality? For example, i'm trying to build a simple (and very approximate) computer simulation of experiment. Now ...
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1answer
28 views

Does the relative angular momentum of the nucleons contribute to the spin of the nuclei?

Imagine we have a nucleus. We do talk about spins of nuclei. Is this spin the total angular momentum of the nucleus, that is, spins and relative angular momentum of all of the nucleons? If so, why? ...
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Spin via Change of Phase

Thinking of spin as arising from a change in the phase of a wave function: The angular momentum is defined by the change of the phase of the wave function under rotations, which may come from the ...
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2answers
202 views

Has magnetism been experimentally demonstrated at the quantum level?

I've learned that magnetic fields are generated by electric currents, and that electric current is the motion of electrons and stuff like that. Many textbooks also talk about "point charges" and have ...
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2answers
161 views

What does the Schrodinger Equation really mean?

I understand that the Schrodinger equation is actually a principle that cannot be proven. But can someone give a plausible foundation for it and give it some physical meaning/interpretation. I guess ...
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25 views

How does a photon travel through an electron cloud?

We all know that the exact position and exact velocity of an electron in an atom cannot be determined simultaneously, as per the Heisenberg uncertainty principle. We only talk about the probability of ...
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18 views

Quantized modes of EM field in a cubic cavity

I am trying to solve for Electric field modes in a cubic cavity with perfectly reflecting walls. I know that for the modes, I have the standard Helmholtz Equation $$(\nabla^2+k^2)E_i=0$$ And I want ...
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29 views

compressibility of cold atoms in optical lattices

The compressibility of cold bosons in an optical lattice is defined as $\kappa = \frac{\partial \langle n\rangle}{\partial \mu}$, where $\langle n\rangle$ is the density and $\mu$ is the chemical ...
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43 views

Imaginary Angular Momentum [on hold]

I recently came across a problem online where it asks you to interpret an imaginary angular momentum about an axis. Apparently there's a chance it has to do with superconducting. What is the correct ...
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61 views

Quantum Harmonic Oscillator - Normalizability of Annihilated Ground State

The common line of deductions in the operator analysis of the quantum harmonic oscillator goes something like this: It is derived that the action of the annihilation operator $a$ on an eigenfunction ...
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45 views

Is there any defect in Rutherford's atomic model according to quantum theory?

According to quantum mechanics charged bodies do not emit energy. Then why the atomic model of Rutherford has the defects of collapsing nucleus, continues spectrum.
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26 views

quantum hall effect and hamiltonian [on hold]

I need a good book or lecture on quantum hall effect. my supervisor wants me to find the Hamiltonian for the Qunatum hall effect, he want me to find this from this relation if it looks like a 2nd ...
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1answer
54 views

References on experimental realization of quantum one-dimensional infinite-well model

Can someone point me to the examples, or references, of experimental realization of the quantum one-dimensional infinite-well model? [EDIT] The motivation of this question is the curiosity - though ...
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46 views

Why does this condition ensure that the residue of the propagator is 1?

The corrected propagator is given by $$\Delta'(q)=\frac{1}{q^2+m^2-\Pi^*(q^2)-i\epsilon}$$ ($\Pi^*$ is the sum of all irreducible one-particle amplitudes) I get that the residue of the original ...
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1answer
43 views

Dirac Notation Question Appearing In a Projection

So I have a part of the energy eigenvalue equation that look like this: $$ \delta(\hat{x})|n\rangle $$ Where n is the energy basis of the Hamiltonian I'm considering. To deal with this, I tried ...
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78 views

When is quantum optics “correct”?

What is the regime under which we may consider quantum optics description of light a good approximation of a more correct theory such as QED? By quantum optics I mean describing the electromagnetic ...
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40 views

Why does the raising and lowering operator not affect total angular momentum?

My notes define: $$ L_{\pm} = L_{x} \pm i L_{y} $$ and states: $$ [L_{z},L_{\pm}] = \pm \hbar L_{\pm} $$ I'm fine with this as it's easy to show the result with some ugly algebra. It then says: ...
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47 views

Stern-Gerlach experiment theory question [on hold]

I have an assignment problem which I've been having some difficulty with. i know the answer but I want to know how to arrive at it correctly, and want to know where I've gone wrong. Determine the ...
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1answer
65 views

Understanding the Particle Data Group review documents

Would someone mind outlining what each piece of semi-structured data means in these images taken of some PDG documents? As a newcomer it is very difficult to interpret the tables. tl;dr This ...
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2answers
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How does an electron move around in an orbital? Is it “wave-like” or random?

When an electron is moving around in it's orbital, is it actually moving around like a wave, like this video shows? (By wave-like, I mean, the "electron" in this video is showing it following a ...
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4answers
138 views

How does the electron jump across “gaps” in its orbital?

I saw on perhaps COSMOS, and have heard mention from other professors, that electrons sort of "teleport" or something, in their orbital and the quantum level. So looking at the orbitals for a lone ...
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1answer
63 views

Coupled Quantum Harmonic Oscillator

Given the following Hamiltonian for two identical linear oscillators with spring constant $k$ and interaction potential $\alpha x_1x_2$; I was asked to find the expectation value $\langle ...
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1answer
40 views

Why is the full eigen function is product of eigen functions and not addition?

For example suppose there is a two electron system. Why is the full eigen function product of the spatial eigen function and spin wave function for the two electron system?
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Time and particles [on hold]

What it is in basic particles that make them propagate themselves through time or, basically, what brings that property known as Duration in a particle (wave)? I sense that this is somehow is based ...
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1answer
97 views

Question about atom subshells

So my teacher told me that EACH shell contains 5 subshells (s, p, d, f, g) but what I don't understand is this The 1st shell has only 1 subshell (and not 5 like he said) and the number of ...
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2answers
31 views

Bound states, scattering states and infinite potentials

I am doing my first semester of Quantum Mechanics and we're using Griffith's Introduction to Quantum Mechanics. As he is introducing the Dirac delta function potential he explains bound and scattering ...
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1answer
40 views

Eigenfunctions for $1s$ hydrogen Schrodinger equation

I am a computer scientist and started my Phd in material science. The second course os my Phd is material simulation by computer. One the task is show the verification of the eigenfunction $1s$ from ...
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2answers
117 views

Is there any physical quantity that does not have uncertainty?

I saw this video and I got a thought: Is there any physical quantity that does not have uncertainty? Basic models are: for lenght for time end energy (so for mass too) and I realized that ...
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4answers
186 views

How did photons and electrons arise out of the quark-gluon plasma?

I am just beginning to learn about the ideas of the early universe, so this is probably a beginner question. I understand that protons and neutrons (which are baryons, which are hadrons) are made out ...
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26 views

Stimulated emission and coherence

For a significant part of my life I have been taught that, if a photon of the "correct" energy meets an excited atom, the atom will then (with a certain probability) undergo transition to a lower ...
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1answer
138 views

Directional derivatives in the multivariable Taylor expansion of the translation operator

Let $T_\epsilon=e^{i \mathbf{\epsilon} P/ \hbar}$ an operator. Show that $T_\epsilon\Psi(\mathbf r)=\Psi(\mathbf r + \mathbf \epsilon)$. Where $P=-i\hbar \nabla$. Here's what I've gotten: ...
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33 views

Simplest Hamiltonian for 2d wave equation with periodic boundary conditions

I want to use the 2d wave equation ($\frac{\partial^2u}{\partial t^2}=\frac{\partial^2u}{\partial x^2}+\frac{\partial^2u}{\partial y^2}$) with periodic boundary conditions as a simple toy model of a ...
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100 views

A question on quantum computing and de Broglie's pilot wave theory

I don't know much about quantum computing except what I have read about on wiki and popsci. I have been reading about the de Broglie-Bohm pilot wave theory and how they describe quantum mechanics in ...