Tagged Questions
5
votes
2answers
92 views
Quantum Mechanical Operators in the argument of an exponential
In Quantum Optics and Quantum Mechanics, the time evolution operator
$$U(t,t_i) = \exp\left[\frac{-i}{\hbar}H(t-t_i)\right]$$
is used quite a lot.
Suppose $t_i =0$ for simplicity, and say the ...
2
votes
0answers
37 views
What is three-photon interference?
Whilst reading this paper on a quantum processor that performs a type of matrix computation, I came across the concept of 'three-photon interference'. A quick Google search shows that this process is ...
2
votes
1answer
38 views
State emitting from an extended thermal source
This calculation is for a double slit experiment setup which is experiencing a far field radiation from an extended monochromatic thermal source. I assume the source is 1-D and it's length is $b$. ...
0
votes
0answers
31 views
Physical significance of effective wave function
In Yanhua Shih's book on quantum optics, the coherence functions are expressed in terms of effective wave function. Here are the expressions for single photon wave packets.
To derive the coherence ...
6
votes
1answer
180 views
Can a photon exhibit multiple frequencies?
Can a photon be a superposition of multiple frequency states? Kind of similar to how an electron can be a superposition of multiple spin states.
0
votes
1answer
52 views
First order coherence through double slit
The state $$|\Psi \rangle = |0\rangle + \sum_j \int d\omega f_j(\omega)\hat{a}^\dagger_j (\omega) |0\rangle $$ is coming from a far field and incident on a double slit setup. Here j is the index of ...
1
vote
1answer
51 views
double slit experiment with two opposite quarter waveplates
Consider the usual double slit experiment involving laser and a double slit and a screen. Now place in front of the left slit a quarter waveplate (let's call it QWP1) that changes a certain linear ...
5
votes
1answer
171 views
What is the “direction” of the transition dipole moment? (Understanding Eq. 9.29, Charge and Energy Transfer 3rd Ed, May & Kuhn)
For a real vector $\mathbf{r}$, the direction is given by: $\hat{\mathbf{n}}=\mathbf{r}/\left|\mathbf{r}\right|$.
The transition dipole moment is a complex vector. How do you define its direction?
...
0
votes
0answers
9 views
Image formation [duplicate]
What is the real cause behind the formation of an image? It is explained as" when rays of light focus at a point image is formed." So here we have two events, one focusing of light and another ...
0
votes
1answer
79 views
Stark effect in two level atomic system
In a two level atomic system ( rabi oscillating problem) the perturbative potential is oscillating / sinusoidal because it comes from the electric field from the laser.
Now stark effect is the ...
0
votes
0answers
39 views
Photon detection rate for pure / mixed states coming from single mode point source
Let the pure states be in superposition of horizontal and vertically polarized basis states. They are arriving at the point detector one at a time. So, a pure state is $|\Psi\rangle = \alpha|V\rangle ...
3
votes
0answers
70 views
Dyson Series Second Order Term Importance vs. Time
Given a time ordered Dyson series expansion of
$$H_I=e^{-\frac{i}{\hbar}\sigma_3t}V_0\sin(\omega t)\sigma_1e^{\frac{i}{\hbar}\sigma_3t}$$
$${\cal ...
0
votes
0answers
102 views
Polarization photon and Stokes parameters
I have the following situation: About the polarization of the photon, I introduce the basis:
Horizontal polarization $|\leftrightarrow>=\binom{1}{0}$
Vertical polarization ...
1
vote
0answers
76 views
How to calculate radiative transition rate of exciton in a quantum dot with specific dimension?
I am writing rate equations for a nanophotonic system including three quantum dots. I need to calculate that radiative transition rates of exciton in ground state in those quantum dots.
In the paper ...
1
vote
0answers
53 views
fiber optic second order PMD as an operator on the tensor product Hilbert space
Second order polarization mode dispersion (SOPMD) is a coupling mechanism between polarization and frequency. Take our photon to be the following tensor product:
$\psi = \int \gamma_{\omega} | ...
0
votes
0answers
203 views
Intensity of the diffraction pattern of the double slit
I am trying another approach for my last unanswered question. (Bounty still on for 3 days. Anyone? Please?) Note that this is not the same question but a greatly simplified version concerning a much ...
2
votes
2answers
198 views
Is there a simple approximation to calculate the index of refraction of water?
A very rough approximation from first principles, from the elementary charge and hbar, would suffice. But is there such an approximation at all?
(Alternatively, if water is too difficult: is there ...
2
votes
1answer
278 views
What IS reflection?
How does quantum electrodynamics actually explain HOW reflection occurs on a microscopic scale?
Note that Feynman's QED lecture series/book is not sufficient, as he only assumes that light DOES ...
0
votes
0answers
103 views
Atomic Coherence(Polarization) of Two Dipole-Dipole Coupled Atoms
My question is about generalization of most simple problem in semi-classical quantum optics. Composite system of two-level systems.
single system's diagram
where atomic frequency: wab=wa - wa; ...
2
votes
1answer
160 views
Validity of Einstein Coefficient Derivations
Consider a two-level energy gap with electronic energy states $E_1$ & $E_2$ and associated population densities $n_1$ and $n_2$ with $E_2>E_1$.
In the derivation of the Einstein coefficients ...
6
votes
3answers
423 views
Computer game with quantum optics / quantum information
Is there a computer game using principles of quantum optics or quantum information?
By game I mean not just a simulation or an interactive course, but something than can be played in an enjoyable ...
5
votes
2answers
56 views
Heuristics for definitions of open and closed quantum dynamics
I've been reading some of the literature on "open quantum systems" and it looks like the following physical interpretations are made:
Reversible dynamics of a closed quantum system are represented ...
3
votes
1answer
131 views
Can spatial coherence be maintained in fiber optic cables over time?
I am doing research with a double slit experiment, using a beam splitter and 2 lengths of fiber optic cable, whose ends brought close together form the effective double slit. I notice that the ...
2
votes
2answers
254 views
Why does optical pumping of Rubidium require presence of magnetic field?
The optical pumping experiment of Rubidium requires the presence of magnetic field, but I don't understand why.
The basic principle of pumping is that the selection rule forbids transition from ...
1
vote
1answer
154 views
Quantum Cryptography
First question was a little bit ambiguous.
Photons are passed through a linear polarizer that is oriented $\theta$ degrees again the photon passes through another linear polarizer that also have a ...
0
votes
2answers
442 views
quantum optics of a polarizing beam splitter
I would like to use the Heisenberg picture in quantum field theory to model a polarizing beam splitter. Is there an easy way for someone to show me how the field operators ($a^\dagger_{input1}$, ...
8
votes
2answers
195 views
What are some ways to (approximately) symbolically diagonalize Hamiltonian operator?
Specifically the Hamiltonian takes the form of
$$\hat H = \frac{\Delta }{2}{\hat \sigma _z} + {\omega _1}\hat a_1^\dagger {\hat a_1} + {\omega _2}\hat a_2^\dagger {\hat a_2} + {g_1}\left( {{{\hat ...
17
votes
2answers
896 views
Rigorous justification for rotating wave approximation
Whenever I have encountered the rotating wave approximation, I have seen "the terms that we are neglecting correspond to rapid oscillations in the interaction Hamiltonian, so they will average to 0 in ...
2
votes
1answer
426 views
What are the polarization states of the photons in a polarized and unpolarized light?
The photons are completely polarized, i.e their polarization states can be expressed as $a|R\rangle+b|L\rangle$, where $|R\rangle$ and $|L\rangle$ are two helicity eigenstates of the photon. For ...
3
votes
1answer
171 views
Linearizing Quantum Operators
I was reading an article on harmonic generation and came across the following way of decomposing the photon field operator.
$$ \hat{A}={\langle}\hat{A}{\rangle}I+ \Delta\hat{a}$$
The right hand side ...
7
votes
2answers
178 views
Finding the spectrum of a polynomial of the creation and annihilation operators
Is there a general algorithm to find the spectrum of $S S^\dagger$, where $S$ is a homogenous polynomial (of degree $n$) of the annihilation operators (of $d$ variables)?
3
votes
2answers
301 views
The most price-efficient experimental setup involving SPDC, single-photon counting etc
I would like a suggestion on a price-efficient way of experimenting with spontaneous down-conversion and single-photon counting. The simple dual-slit experiment could be one part of an application ...
2
votes
0answers
118 views
Do Bell inequality violations appear instantly when the source is turned on, or do they increase over time?
This experimental Question is a result of reading a particular article on Bell violations. I addressed the e-mail below to the corresponding authors —because who knows, they might reply— but it is not ...
3
votes
0answers
184 views
back-action noise
I recently have come across with two key-concepts: shot noise and back-action noise in quantum optics. This is very important for me to know: first, are shot noise and back-action the same? Please let ...
4
votes
2answers
152 views
Does the Casimir effect allow to change the lifetime of a radiating atom?
Is it true that a spontaneously light-emitting atom changes its lifetime if it is put between two parallel plates that are so near that they attract each other through the Casimir effect?
Thus: does ...
16
votes
5answers
2k views
Does a photon interfere only with itself?
I sometimes hear statements like that:
Quantum-mechanically, interference pattern occurs due to quantum interference of wavefunction of a photon. Wavefunction of a single photon only interferes ...
0
votes
1answer
266 views
What is the spectral energy density of virtual photons around a unit charge at rest?
Given that my previous question, namely "What is the number density of virtual photons around a unit charge?" has no precise answer, here is a more precise wording:
What is the virtual photon ...
2
votes
2answers
409 views
Scalar product of coherent states
We suppose for semplicity to have a 1D oscillator, but this is a question abaout the general CCR algebra in oscillators, second quantization, quantum field theory etc.
We know coherent states are a ...
6
votes
3answers
951 views
Photon wave packets from distant stars
A distant star like the sun, thousands of light years away, could be so faint that only one photon might arrive per square meter every few hundred seconds. How can we think about such an arriving ...
3
votes
2answers
449 views
Alkali atom - photon interaction in zero magnetic field
An alkali atom has a single outer electron that interacts with incoming photons of the right wavelength (for alkalies it's in the visible & IR range). If there is an external magnetic field, the ...
0
votes
1answer
935 views
Explanation of the experiment with Mach–Zehnder interferometer (self-interference of a single photon)
Here is the description of experiment which uses Mach–Zehnder interferometer
http://en.wikipedia.org/wiki/Mach-Zehnder
or
http://departments.colgate.edu/physics/research/Photon/root/ajpbs02.pdf
...
10
votes
2answers
523 views
Unambiguous distinguishing of quantum states by local measurement
Let's have two orthogonal n-particle quantum states: $|\psi \rangle$ and $|\phi \rangle$. In theory it is always possible to make an unambiguous measurement.
However, things get complicated when one ...
