A research field within general optical physics concerned with light and its material interaction: where light is modelled by full quantum mechanical description.

learn more… | top users | synonyms

1
vote
0answers
24 views

damped quantum harmonic oscillator - evolution of coherent state

I am trying to solve the following Master equation (also similar to damped quantum harmonic oscillator): $$\frac{d\hat{\rho}}{dt} = \frac{\Gamma}{2}\left(2\hat{a}\hat{\rho}\hat{a}^{\dagger} - ...
1
vote
2answers
104 views

How to represent a laser pulse in quantum optics

Every quantum optics textbook that I've found says something like "a coherent state represents the output of a laser", but a coherent state is a static thing (aside from the oscillating phase of the ...
1
vote
0answers
19 views

Wigner functions, symmetry

I'm trying to get more insight into quasiprobability distributions, as for example the Wigner function. There are some Wigner functions, which are symmetric. Symmetric: Fock state Thermal states ...
3
votes
0answers
38 views

Wave vector relation in nonlinear material

A light wave ($k_1,\omega_1$) travels in a medium of refractive index $n_1$ and then encounters a nonlinear medium ($n_2$) under the angle $\theta_1$. Snell's law tells us the wave's direction in the ...
1
vote
0answers
48 views

What is the reason behind total internal reflection?

I know that when we increase i , r increases unevenly, i.e i increases a little but r increases with a greater amount. At some time, when i reaches the critical angle, r becomes 90 and if we further ...
3
votes
2answers
117 views

Annihilating coherent state

Starting facts Annihilation operator $a$ removes one photon from fock state. Coherent states are eigenstates of annihilation operator and they are also superposition of different fock states. This ...
3
votes
1answer
229 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 ...
0
votes
1answer
37 views

Atomic system satisfying a simple level scheme

I have a simple two level system with an allowed dipole transition between the levels. The top level is also allowed to decay to another third level (looks a bit like a lambda system). Could someone ...
0
votes
0answers
62 views

Exact meaning of “pi/2 pulse”

In studying Mach-Zehnder and Ramsey interferometers, I came across the expression "$\pi/2$ pulse". What does it mean exactly? I am working with a Bloch vector representation $(u,v,w)$ of a 2 state ...
0
votes
0answers
32 views

Multi-photon excitation probability for a two-level system

If a two-level system with a lifetime $\tau$ is excited with a pulse of duration $t_{pulse}$, what is the probability of exciting more than one photon? For simplicity we can take it to be a $\alpha ...
1
vote
2answers
67 views

Varying the Predictability in a Double Slit Experiment

I know that the Englert-Greenberger-Yasin Duality Relation states that as the predictability of finding a photon at a slit in a double slit experiment increases, the visibility of the interference ...
0
votes
0answers
25 views

What exactly makes transmittance of graphene change from linear to exponential?

Up to 5 layers, the transmittance of graphene is linear (2.3% per layer): (source) Beyond 5 layers (I assume) the transmittance is exponential, following Beer–Lambert law. What gives rise to this ...
2
votes
1answer
72 views

What is a quasi-probability distribution?

I have some questions about the quasi-probability distribution. What is it? And why it is important in quantum mechanics? And what does "quasi" mean?
4
votes
1answer
99 views

Transformation of Jaynes-Cummings Hamiltonian

This is the Jaynes-Cummings Hamiltonian in the interaction picture: $H_i^n = \hbar g \sqrt{n+1}\begin{pmatrix} 0 & \exp(-i\delta t)\\ \exp(i\delta t) & 0 \end{pmatrix}$ I want to transform ...
0
votes
0answers
6 views

Reason for the difference between Photoluminescence and RAMAN widths

I am measuring the Photoluminescence and RAMAN spectra of a few samples but am unable to understand one thing, why are the width of the photoluminescence bulges so broad while the width of the RAMAN ...
1
vote
1answer
64 views

What is the different between a dark state and a ground state?

In a atomic quantum system, typically discussing in quantum optics, there is something called dark state. A dark state is a state of a quantum system that does not emit any photon. A ground state also ...
1
vote
0answers
52 views

What happens to the Fringe Width when the velocity of electrons passing through the slit in Young's Double Slit Experiment increases?

A beam of electron is used in Young's Double Slit Experiment. The slit width is d. Then the velocity of electron is increased. What happens to the Fringe Width? My approach: $$\beta = ...
1
vote
1answer
34 views

How the Jordan Schwinger components transform the mode operators in a Beam Splitter- component

Hello, I am unsure how to prove this equation. It is suggested to take the derivative with respect to theta on both sides and use commutation relations for the Jordan Schwinger operators. I can't ...
3
votes
0answers
70 views
4
votes
3answers
4k views

Lasing in a 2-Level system?

What exactly is the difference between 2-Level, 3-Level and 4-Level systems? Why can we not achieve stimulated emission in a two-level system using optical pumping?
0
votes
1answer
38 views

Varying the Relative Amounts of Light Passing Through Each Slit in the Double Slit Experiment

What happens if different amounts of light pass through each slit in the double slit experiment? For example, if twice as much light passed through one slit as through the other slit, how would the ...
0
votes
1answer
28 views

Computing covariance matrix of two mode state?

Suppose that I want to calculate the covariance matrix of the state of modes $A$ and $C$ with quadrature $(x_a, p_a)$ and $(x_b,p_b)$ . But instead of the state in order to calculate all expectation ...
2
votes
2answers
92 views

The definition of Gaussian State

Could you clarify to me what is a Gaussian state? I know what is a Gaussian function and Gaussian distribution, but I don't know how to respond to other when they ask me to provide the definition of a ...
0
votes
0answers
37 views

Can thermal states of light be monochromatic?

As one can read from the quantum optics textbooks each mode of light of a certain frequency, spatial configuration and polarization can be considered as a quantum harmonic oscillator. One can imagine ...
0
votes
0answers
27 views

element effect on quantum dot band gap

Main Question: Why do Au QDs have quantum confinement effects which change optical behavior from the bulk Au, whie certain other elements (such as Fe) are typically not shown to have the same ...
1
vote
1answer
79 views

Diagonalizing a linearized optomechanical Hamiltonian

in the paper Nonlinear Interaction Effects in a Strongly Driven Optomechanical Cavity, the authors diagonalize the Hamiltonian (equation (2) in the paper) $$H_1=−Δd^†d+ω_Mb^†b+G(d+d^†)(b+b^†)$$ in ...
0
votes
2answers
48 views

Quantum Crypto infrastructure & hardware

To implement real quantum cryptography in the real world, does the physical link layer from Point A to Point B be an optical link for all parts? Is there any links or whitepaper containing prototypes ...
1
vote
1answer
40 views

What is the exact mechanism in line broadening of transition frequencies?

I've been having trouble understanding why transition lines in unperturbed states are not infinitely narrow. I'll run through my reasoning and hopefully that helps find the flaw. I imagine that if we ...
0
votes
0answers
29 views

How could you match the phase of two waves?

Imagine the Mach-Zehnder interferometer with split beams of a laser guided in a way that would result in constructive interference in one direction and destructive interference in the remaining ...
1
vote
1answer
46 views

Is there a beam splitter in time?

I have a train of pulses (with some known time separation between them) and I want to mix two of these (perform an XOR - beam splitter transformation - between them), leaving the rest alone. How do I ...
1
vote
2answers
104 views

Maxwell equations and quantized electromagnetic field

When the electromagnetic field is quatized for a single mode, we first take Maxwell equations and proceed to write the electric and magnetic field as a stationary wave, since we consider the ...
2
votes
0answers
32 views

How is the temporal coherence of a pulse defined?

I am having problem with the concept of coherence and photon degeneracy. The temporal coherence of pulse is defined in Born and Wolf as: $$t_c=\lambda^2/c\Delta\lambda$$ (The time a photon takes to ...
0
votes
1answer
36 views

Stimulated emission role in laser cooling

Laser cooling can be achieved by exciting an atomic system, in order to "pump" atoms in the excited state. This gives a recoil momentum $\hbar k$ the the atom, which then emits spontaneously. As ...
1
vote
1answer
29 views

Interpretation of different values of antibunching

When the frequency resolved second order correlation function at zero time delay, $$g^{(2)}(\omega_1, \omega_2) = \frac{\langle a_1^\dagger a_1(t) a_2^\dagger a_2(t)\rangle}{\langle a_1^\dagger ...
0
votes
2answers
223 views

Alternate Young double slit experiment

What will happen in Young's double slit experiment, when instead of screen I put a black screen with a hole and a second screen behind the black one. Will it still form interference pattern albeit a ...
1
vote
1answer
61 views

Why does the discussion in a certain reference frame gives us the correct physics?

The question: whenever you are dealing with quantum optics you will encounter a lot of unitary transformations very soon. A question that is in my mind for quite a long time is: Why does the ...
1
vote
2answers
124 views

Do photons emitted from a LED show bunching?

If photons are emitted from a thermal source, we get photon bunching. For coherent radiation, the detection probability doesn't change after detecting a photon. For single photon sources, we get ...
0
votes
0answers
12 views

Is the truncated Wigner method efficiently classical simulatable?

The continuous-variable Gottesman-knill theorem says that the operation which varying the initial state described as the gaussian function (such as vacuum) to the final state described as the gaussian ...
0
votes
1answer
36 views

Are there any other tests demonstrating wave properties besides interference and diffraction?

Are there any other tests demonstrating wave properties besides interference and diffraction? How about refraction? Does it show wave properties also?
9
votes
6answers
1k views

Are coherent states of light 'classical' or 'quantum'?

Coherent states of light, defined as $$|\alpha\rangle=e^{-\frac{|\alpha|^2}{2}}\sum_{n=0}^\infty \frac{\alpha^n}{\sqrt{n!}}|n\rangle $$ for a given complex number $\alpha$ and where $|n\rangle$ is a ...
0
votes
1answer
56 views

Time multiplexed detector - pulse dispersion - foruier limits.

I'm currently in my second semester in physics and a couple of weeks ago I saw a job offer in the optics department of my university. Although I don't know much about optics, since we didn't deal with ...
2
votes
2answers
113 views

Entanglement of coherent states

I am new to quantum optics and I am trying to understand whether coherent states of the field could be entangled. Let's consider, for example, a two-mode state: $|\psi^{AB} \rangle = \frac{1}{c} ...
3
votes
1answer
128 views

Electron momentum distribution and wavefunction in momentum space

Does there exist any relationship between the electron momentum distribution used in above threshold ionization and the wave function in momentum space? In other words, starting with the wavefunction ...
4
votes
4answers
233 views

Are photons inside the media massive? If yes, why there is no Meissner effect?

We all know in vacuum travels with speed $c$, hence its rest mass has to be 0. In the media the light speed $v<c$. Then the photon renormalized by the medium (call it "quasi-photon" if you like), ...
11
votes
1answer
343 views

Which qubit states are accessible with linear optics operations?

Given a quantum state of $n$ qubits, and being restricted to linear optics (that is, the output annihilation operators are linear combinations of the input annihilation operators): Which states are ...
5
votes
1answer
344 views

Output of a beamsplitter with photon number (Fock) state inputs

Given a beamsplitter drawn below, where $\hat{a}$ and $\hat{b}$ are input modal annihilation operators, transmissivity is $\tau\in[0,1]$, and output modal annihilation operators are ...
0
votes
0answers
37 views

Is there a theoretical derivation of Kim's delayed choice quantum eraser?

Is there a theoretical derivation of Kim's delayed choice quantum eraser? The original paper only shows the experimental data.
0
votes
0answers
65 views

Gain clamping and threshold gain in quantum optics

We increase the pump power of a laser to the point where laser action starts, i.e. the threshold gain is reached. Now we increase the pump power even more, which increases the intensity of the cavity ...
3
votes
3answers
140 views

'size' of a photon

What's the smallest apperture a photon can pass through? I mean with no transmission at all. I'm pretty sure I saw long ago an experiment when they were reducing the size of a hole in a gold film and ...
2
votes
1answer
645 views

Obtain the Lagrangian from the system of coupled equation [closed]

In this particular paper, "Interaction between a moving mirror and radiation pressure: A Hamiltonian formulation" by C.K.Law, PhysRevA.51.2537 \begin{equation} ...