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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Parity conservation in second harmonic generation?

The second harmonic arises from susceptibility of third rank tensor $X^{(2)}$ which have (-1) parity. page 28 Let say two photons are absorbed and one is emitted, so the total change in parity is ...
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42 views

Gaining some intuition: Photon bunching

This is a very easy question: I'm in need of some intuition on the fact that, e.g. thermal sources, produce bunched photons. It is very easy to "undertand", without any quantum mechanics, why single ...
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86 views

Von Neumann entropy of mixtures of coherent states

I'm trying to calculate the Von Neumann entropy of statistical mixtures of coherent states. The problem is that such states are in general non-Gaussian, so one cannot follow the formalism developed ...
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How to find the correlation function? [on hold]

I have an operator $\hat{a}(t)$, and the its correlation is given as: $$\langle\hat{a}(t)\hat{a}^{\dagger}(t^{\prime })\rangle=\delta(t-t^{\prime})$$ Then how can I find the correlation function in ...
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33 views

Is Mott insulator the same as non-compressible quantum fluid?

In the field of ultracold quantum gases we study the so called Bose-Hubbard model given in second quantization: $$\hat{\mathcal{H}} = -t\sum_{\langle i,j\rangle}\hat{a}^{\dagger}_{i}\hat{a}_{j} + ...
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30 views

Reaching equilibrium in a blackbody and light-matter interaction

Suppose we have a metallic cavity maintained at a fixed temperature. Suppose we start with any distribution of radiation that is not in equilibrium with the container. Gradually, when the equilibrium ...
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13 views

noise spectral density of squeezed vacuum ? [closed]

What is the noise spectral density of the squeezed vacuum? Assume: Squeezed vacuum is generated via parametric amplifier. Squeeze angle is zero, squeeze factor R=1.15...
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742 views

Photons with half integer angular momentum - what's happening?

I have just read this article - what is happening? Analysing these beams within the theory of quantum mechanics they predicted that the angular momentum of the photon would be half-integer, and ...
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22 views

Rotating wave approximation for two coupled resonators and a drive

I'm having some trouble with what I think should be an easy calculation. On qutip.org/docs/2.2.0/examples/me/ex-25.html they calculate the steady state for a master equation, more specifically they ...
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21 views

How is the conversion from an operator equation to a c-number stocastic differential equation justified?

In many papers on laser dynamics theory, quantum Langevin equation of operators is converted to c-number stocastic differential equations, which is analyzed to obtain results. However, why this ...
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36 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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32 views

Sech laser pulse time-bandwidth product calculation

Find the time bandwidth product for a $\operatorname{sech}$ shaped pulse. Attempt: I know that the time bandwidth product $\Delta t \Delta \omega$ for a $\operatorname{sech}$ shaped pulse must ...
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596 views

Formula for Rabi frequency

I have calculated the dipole transition elements of electronic states $\langle a|D_1^m|b \rangle$ following the book of Cohen-Tannoudji (Complement $E_X$) and tried then to calculate from that the ...
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58 views

Why probability of detection by performing unambiguous quantum measurement is less than random guess in mesoscopic quantum regime?

In mesoscopic quantum regime (mean photon number 10000) and non-orthogonal coherent state(number of non-orthogonal coherent state 2000), why probability of detection by performing quantum unambiguous ...
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14 views

Why probability of detection of optimum unambiguous discrimination between linearly independent symmetric states is less than random guess? [duplicate]

Considering the analysis and result of this paper, http://arxiv.org/pdf/quant-ph/9807023v1.pdf, I have used equation (3.15) and (4.3) to calculate the optimum probability of success for mean photon ...
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241 views

In quantum optics if you measure the energy of a thermal state does it collapse to a Fock state (Photon number state)?

As I understand it a thermal state is a state of light such that the light is in a superposition of many Fock states (Photon number states) with the probability of the light being found in a ...
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60 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: ...
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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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254 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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41 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 ...
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1answer
32 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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14 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, ...
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86 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 ...
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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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106 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?
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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?
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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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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)?
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983 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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39 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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28 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 ...
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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 ...
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77 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 ...
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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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36 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 = ...
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3answers
369 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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154 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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37 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?
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70 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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112 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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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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61 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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46 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 ...
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152 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 ...
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1answer
58 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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36 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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136 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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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 ...
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144 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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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.