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

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What causes atoms to have their specific colors?

I understand that light (color) is part of the electromagnetic spectrum, and that it depends on what wavelengths are reflected/absorbed. Though what property of an individual atom gives it its color? ...
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1answer
253 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 ...
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0answers
24 views

Is there a minimum population inversion necessary for lasing? [on hold]

Let's say I have a cavity built, with a lasing medium inside, positioned optimally. What are the conditions on the population inversion that must take place for lasing to occur?
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1answer
17 views

Difference between Amplitude and Intensity Interferometer?

A lot of books explain the first order and second order coherence correlations for light. They explain the difference between these using interferometers (Michelson and Hanbury-Brown and Twiss (HBT) ...
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31 views

Second Order Coherence of NOON State

Given the entangled state $\vert NOON \rangle =\frac{1}{\sqrt{2}}(\vert N,0\rangle + \vert 0,N\rangle)$ how can the second order coherence function at time $\tau$ and 0 be calculated? I know that ...
3
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1answer
25 views

Master equation approach only suitable for good cavity laser?

As I understand, master equation and quantum Langevin equation are equivalent formalisms. However, in a Review of Modern Physics article titled sub-Poissonian processes in quantum optics, the author ...
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0answers
11 views

Resonance Fluorescence spectrum of a symmetric state of two atoms

So recently I've learned about the fluorescence spectrum of an atom (say a two level system) driven by a laser close to its resonance frequency. You get a dressing of the atom states with the laser, ...
2
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1answer
70 views

What exactly happens when total internal reflection takes place at a quantum level?

What happens when light interacts with the boundary between 2 mediums at a quantum level? Why is it totally reflected back when it is travelling from an optically denser to a less dense medium? How ...
2
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1answer
55 views

How to transform a wigner function to represent loss of mode information (coarse graining)?

I have a highly multi-mode gaussian wigner function representing an optical field: $$W\left(\{p\},\{q\}\right)=\mathrm{Exp}\left(-\sum_{j=0}^{f}(b_{j}q^{2}_{j}+a_{j}p^{2}_{j})\right).$$ However the ...
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0answers
29 views

Representing operators in the Glauber-Sudarshan P-representation

If $| \alpha >$ represents a coherent state (the normalized right eigenstate of the destruction operator $a$ in Quantum Mechanics; $\alpha$ is a complex number), then it is known that: ...
2
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1answer
97 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?
6
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4answers
5k 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?
3
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54 views

Beam Splitter: looking for a “not-typical” second quantization but full-quantum description

In all the books of Quantum Optics I read, the theory of beam-splitter (BS) is presented in more or less the same way, e.g. introduction of the transmission-reflection matrix, case study of the single ...
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1answer
40 views

What is the easiest way to prepare a Glauber coherent state? [closed]

Without using a laser source. Can you, for example, create a coherent state by filtering another light source (incandescent light bulb, LED, etc)?
11
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2answers
976 views

Reference request: Susskind-Glogower original paper

I'm trying to find Susskind and Glogower's original paper, L. Susskind and J. Glogower. Quantum mechanical phase and time operator. Physics 1 (1964) 49-61 where they propose their exponential ...
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0answers
35 views

How do pulse properties relate to the pulse's peak power?

Let's say we know the temporal shape of an optical pulse, which is $E(t) = E_0 \cdot f(t)$, where $E(t)$ is the electric field, $E_0$ its amplitude and $f(t)$ the shape function (e.g. $sech^2$, ...
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0answers
26 views

Vaccuum expectations for a string of creation and annihilation operators

I want to determine the vaccum expectation value of a string of creation and annihilation operators. They have a very specific form: $$\langle \prod_{i=1}^n \hat{a}(k_i) \, \, \hat{N}_1 \prod_{j=1}^n ...
3
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3answers
988 views

Is there a way to increase the speed of light itself?

When light enters materials it slows down due to its refractive index (due to absorbing and re-emission of photons). But, is there a way to increase the speed of light itself? Can there be some ...
2
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1answer
75 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 ...
15
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3answers
2k views

How is squeezed light produced?

Ordinary laser light has equal uncertainty in phase and amplitude. When an otherwise perfect laser beam is incident onto a photodetector, the uncertainty in photon number will produce shot noise with ...
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0answers
32 views

Can a simple harmonic oscillator describe Rabi oscillations?

I've been trying to simulate a resonant laser oscillation of a two level atom with Rabi frequency $\Omega$ and a rate of spontaneous emission $\Gamma$. So the wavefunction would be $\mid \Psi\rangle = ...
4
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3answers
360 views

Relation between representations of boson operators?

I have a simple (I think !) question about the representations of boson operators and how they are related. First of all let's define two conjugate observables $Q$ and $P$ (i.e. $\left[Q,P\right]=i$ ...
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0answers
29 views

Definition effective nonlinear coefficient (SHG)

For a course in Electro Optics I have to do a home assignment. Given is that the input field is a plane wave propagating at frequency $\omega$ in the $y$-direction and polarized in the $(x,z)$ plane. ...
6
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2answers
152 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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1answer
30 views

Why “vacuum” in vacuum Rabi splitting (VRS)?

What is the role of "vacuum" in vacuum Rabi splitting (VRS)? Also, does VRS arise because of quantized nature of light? If not, what is a semiclassical explanation for VRS?
3
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1answer
63 views

Normal Ordering and Smearing

I read on Wikipedia two different descriptions of the "Husimi-Q representation." One is that it is the Wigner function convolved with a Gaussian, which in particular results in a positive definite ...
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1answer
91 views

SPDC and single photon production

In Spatial Parametric Down Conversion, incoming photons are split into entangled photon pairs by passing through a non-linear optical medium. Since I get a photon pair as an output then how can I say ...
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0answers
53 views

Generating Single photons

How can single photons be generated by making a coherent state weaker by attenuating it?(For reference please see, Quantum Computation and Quantum Information by Nielsen and Chuang, 10th ...
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1answer
60 views

How to include temperature effect in optical bloch equations (optical pumping)?

My problem is about the optical pumping of Alkali atoms by circularly polarized pump light. Consider a circular polarized light ($\Delta m=+1$) $$\vec{E}(z,t)= \vec{E}^{(+)}_0 e^{-i\nu t}+c.c. $$ ...
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1answer
41 views

generating function method for expectation values of operator products

Many times in quantum physics we face a problem of calculating expectation values of normal product operators. Assume we have a two level system with creation and annihilation operators $\hat{a}$ and ...
0
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1answer
129 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 ...
3
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1answer
57 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 ...
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34 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} - ...
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2answers
130 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 ...
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0answers
53 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 ...
5
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2answers
141 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 ...
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1answer
40 views

Gravitational Lensing Example

Can the actual size of a black hole be hidden behind by the photon sphere like this tomato wrapped underwater? Like an eye in a eyelid.
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1answer
41 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 ...
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0answers
39 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 ...
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2answers
70 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 ...
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0answers
27 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 ...
4
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1answer
114 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 ...
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0answers
9 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 ...
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1answer
99 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 ...
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0answers
107 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 = ...
0
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1answer
43 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 ...
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0answers
79 views
0
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1answer
40 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
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1answer
39 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 ...
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2answers
123 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 ...